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linux-zen-desktop/kernel/sched/fair.c

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// SPDX-License-Identifier: GPL-2.0
/*
* Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
*
* Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
*
* Interactivity improvements by Mike Galbraith
* (C) 2007 Mike Galbraith <efault@gmx.de>
*
* Various enhancements by Dmitry Adamushko.
* (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
*
* Group scheduling enhancements by Srivatsa Vaddagiri
* Copyright IBM Corporation, 2007
* Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
*
* Scaled math optimizations by Thomas Gleixner
* Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
*
* Adaptive scheduling granularity, math enhancements by Peter Zijlstra
* Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
*/
#include <linux/energy_model.h>
#include <linux/mmap_lock.h>
#include <linux/hugetlb_inline.h>
#include <linux/jiffies.h>
#include <linux/mm_api.h>
#include <linux/highmem.h>
#include <linux/spinlock_api.h>
#include <linux/cpumask_api.h>
#include <linux/lockdep_api.h>
#include <linux/softirq.h>
#include <linux/refcount_api.h>
#include <linux/topology.h>
#include <linux/sched/clock.h>
#include <linux/sched/cond_resched.h>
#include <linux/sched/cputime.h>
#include <linux/sched/isolation.h>
#include <linux/sched/nohz.h>
#include <linux/cpuidle.h>
#include <linux/interrupt.h>
#include <linux/memory-tiers.h>
#include <linux/mempolicy.h>
#include <linux/mutex_api.h>
#include <linux/profile.h>
#include <linux/psi.h>
#include <linux/ratelimit.h>
#include <linux/task_work.h>
#include <asm/switch_to.h>
#include <linux/sched/cond_resched.h>
#include "sched.h"
#include "stats.h"
#include "autogroup.h"
/*
* Targeted preemption latency for CPU-bound tasks:
*
* NOTE: this latency value is not the same as the concept of
* 'timeslice length' - timeslices in CFS are of variable length
* and have no persistent notion like in traditional, time-slice
* based scheduling concepts.
*
* (to see the precise effective timeslice length of your workload,
* run vmstat and monitor the context-switches (cs) field)
*
* (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
*/
#ifdef CONFIG_ZEN_INTERACTIVE
unsigned int sysctl_sched_latency = 4000000ULL;
static unsigned int normalized_sysctl_sched_latency = 4000000ULL;
#else
unsigned int sysctl_sched_latency = 6000000ULL;
static unsigned int normalized_sysctl_sched_latency = 6000000ULL;
#endif
/*
* The initial- and re-scaling of tunables is configurable
*
* Options are:
*
* SCHED_TUNABLESCALING_NONE - unscaled, always *1
* SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
* SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
*
* (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
*/
unsigned int sysctl_sched_tunable_scaling = SCHED_TUNABLESCALING_LOG;
/*
* Minimal preemption granularity for CPU-bound tasks:
*
* (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
*/
#ifdef CONFIG_ZEN_INTERACTIVE
unsigned int sysctl_sched_min_granularity = 400000ULL;
static unsigned int normalized_sysctl_sched_min_granularity = 400000ULL;
#else
unsigned int sysctl_sched_min_granularity = 750000ULL;
static unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
#endif
/*
* Minimal preemption granularity for CPU-bound SCHED_IDLE tasks.
* Applies only when SCHED_IDLE tasks compete with normal tasks.
*
* (default: 0.75 msec)
*/
unsigned int sysctl_sched_idle_min_granularity = 750000ULL;
/*
* This value is kept at sysctl_sched_latency/sysctl_sched_min_granularity
*/
#ifdef CONFIG_ZEN_INTERACTIVE
static unsigned int sched_nr_latency = 10;
#else
static unsigned int sched_nr_latency = 8;
#endif
/*
* After fork, child runs first. If set to 0 (default) then
* parent will (try to) run first.
*/
unsigned int sysctl_sched_child_runs_first __read_mostly;
/*
* SCHED_OTHER wake-up granularity.
*
* This option delays the preemption effects of decoupled workloads
* and reduces their over-scheduling. Synchronous workloads will still
* have immediate wakeup/sleep latencies.
*
* (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
*/
#ifdef CONFIG_ZEN_INTERACTIVE
unsigned int sysctl_sched_wakeup_granularity = 500000UL;
static unsigned int normalized_sysctl_sched_wakeup_granularity = 500000UL;
#else
unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
static unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
#endif
const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
int sched_thermal_decay_shift;
static int __init setup_sched_thermal_decay_shift(char *str)
{
int _shift = 0;
if (kstrtoint(str, 0, &_shift))
pr_warn("Unable to set scheduler thermal pressure decay shift parameter\n");
sched_thermal_decay_shift = clamp(_shift, 0, 10);
return 1;
}
__setup("sched_thermal_decay_shift=", setup_sched_thermal_decay_shift);
#ifdef CONFIG_SMP
/*
* For asym packing, by default the lower numbered CPU has higher priority.
*/
int __weak arch_asym_cpu_priority(int cpu)
{
return -cpu;
}
/*
* The margin used when comparing utilization with CPU capacity.
*
* (default: ~20%)
*/
#define fits_capacity(cap, max) ((cap) * 1280 < (max) * 1024)
/*
* The margin used when comparing CPU capacities.
* is 'cap1' noticeably greater than 'cap2'
*
* (default: ~5%)
*/
#define capacity_greater(cap1, cap2) ((cap1) * 1024 > (cap2) * 1078)
#endif
#ifdef CONFIG_CFS_BANDWIDTH
/*
* Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
* each time a cfs_rq requests quota.
*
* Note: in the case that the slice exceeds the runtime remaining (either due
* to consumption or the quota being specified to be smaller than the slice)
* we will always only issue the remaining available time.
*
* (default: 5 msec, units: microseconds)
*/
#ifdef CONFIG_ZEN_INTERACTIVE
static unsigned int sysctl_sched_cfs_bandwidth_slice = 3000UL;
#else
static unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
#endif
#endif
#ifdef CONFIG_NUMA_BALANCING
/* Restrict the NUMA promotion throughput (MB/s) for each target node. */
static unsigned int sysctl_numa_balancing_promote_rate_limit = 65536;
#endif
#ifdef CONFIG_SYSCTL
static struct ctl_table sched_fair_sysctls[] = {
{
.procname = "sched_child_runs_first",
.data = &sysctl_sched_child_runs_first,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec,
},
#ifdef CONFIG_CFS_BANDWIDTH
{
.procname = "sched_cfs_bandwidth_slice_us",
.data = &sysctl_sched_cfs_bandwidth_slice,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ONE,
},
#endif
#ifdef CONFIG_NUMA_BALANCING
{
.procname = "numa_balancing_promote_rate_limit_MBps",
.data = &sysctl_numa_balancing_promote_rate_limit,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO,
},
#endif /* CONFIG_NUMA_BALANCING */
{}
};
static int __init sched_fair_sysctl_init(void)
{
register_sysctl_init("kernel", sched_fair_sysctls);
return 0;
}
late_initcall(sched_fair_sysctl_init);
#endif
static inline void update_load_add(struct load_weight *lw, unsigned long inc)
{
lw->weight += inc;
lw->inv_weight = 0;
}
static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
{
lw->weight -= dec;
lw->inv_weight = 0;
}
static inline void update_load_set(struct load_weight *lw, unsigned long w)
{
lw->weight = w;
lw->inv_weight = 0;
}
/*
* Increase the granularity value when there are more CPUs,
* because with more CPUs the 'effective latency' as visible
* to users decreases. But the relationship is not linear,
* so pick a second-best guess by going with the log2 of the
* number of CPUs.
*
* This idea comes from the SD scheduler of Con Kolivas:
*/
static unsigned int get_update_sysctl_factor(void)
{
unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
unsigned int factor;
switch (sysctl_sched_tunable_scaling) {
case SCHED_TUNABLESCALING_NONE:
factor = 1;
break;
case SCHED_TUNABLESCALING_LINEAR:
factor = cpus;
break;
case SCHED_TUNABLESCALING_LOG:
default:
factor = 1 + ilog2(cpus);
break;
}
return factor;
}
static void update_sysctl(void)
{
unsigned int factor = get_update_sysctl_factor();
#define SET_SYSCTL(name) \
(sysctl_##name = (factor) * normalized_sysctl_##name)
SET_SYSCTL(sched_min_granularity);
SET_SYSCTL(sched_latency);
SET_SYSCTL(sched_wakeup_granularity);
#undef SET_SYSCTL
}
void __init sched_init_granularity(void)
{
update_sysctl();
}
#define WMULT_CONST (~0U)
#define WMULT_SHIFT 32
static void __update_inv_weight(struct load_weight *lw)
{
unsigned long w;
if (likely(lw->inv_weight))
return;
w = scale_load_down(lw->weight);
if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
lw->inv_weight = 1;
else if (unlikely(!w))
lw->inv_weight = WMULT_CONST;
else
lw->inv_weight = WMULT_CONST / w;
}
/*
* delta_exec * weight / lw.weight
* OR
* (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
*
* Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
* we're guaranteed shift stays positive because inv_weight is guaranteed to
* fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
*
* Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
* weight/lw.weight <= 1, and therefore our shift will also be positive.
*/
static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
{
u64 fact = scale_load_down(weight);
u32 fact_hi = (u32)(fact >> 32);
int shift = WMULT_SHIFT;
int fs;
__update_inv_weight(lw);
if (unlikely(fact_hi)) {
fs = fls(fact_hi);
shift -= fs;
fact >>= fs;
}
fact = mul_u32_u32(fact, lw->inv_weight);
fact_hi = (u32)(fact >> 32);
if (fact_hi) {
fs = fls(fact_hi);
shift -= fs;
fact >>= fs;
}
return mul_u64_u32_shr(delta_exec, fact, shift);
}
const struct sched_class fair_sched_class;
/**************************************************************
* CFS operations on generic schedulable entities:
*/
#ifdef CONFIG_FAIR_GROUP_SCHED
/* Walk up scheduling entities hierarchy */
#define for_each_sched_entity(se) \
for (; se; se = se->parent)
static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
struct rq *rq = rq_of(cfs_rq);
int cpu = cpu_of(rq);
if (cfs_rq->on_list)
return rq->tmp_alone_branch == &rq->leaf_cfs_rq_list;
cfs_rq->on_list = 1;
/*
* Ensure we either appear before our parent (if already
* enqueued) or force our parent to appear after us when it is
* enqueued. The fact that we always enqueue bottom-up
* reduces this to two cases and a special case for the root
* cfs_rq. Furthermore, it also means that we will always reset
* tmp_alone_branch either when the branch is connected
* to a tree or when we reach the top of the tree
*/
if (cfs_rq->tg->parent &&
cfs_rq->tg->parent->cfs_rq[cpu]->on_list) {
/*
* If parent is already on the list, we add the child
* just before. Thanks to circular linked property of
* the list, this means to put the child at the tail
* of the list that starts by parent.
*/
list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
&(cfs_rq->tg->parent->cfs_rq[cpu]->leaf_cfs_rq_list));
/*
* The branch is now connected to its tree so we can
* reset tmp_alone_branch to the beginning of the
* list.
*/
rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
return true;
}
if (!cfs_rq->tg->parent) {
/*
* cfs rq without parent should be put
* at the tail of the list.
*/
list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
&rq->leaf_cfs_rq_list);
/*
* We have reach the top of a tree so we can reset
* tmp_alone_branch to the beginning of the list.
*/
rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
return true;
}
/*
* The parent has not already been added so we want to
* make sure that it will be put after us.
* tmp_alone_branch points to the begin of the branch
* where we will add parent.
*/
list_add_rcu(&cfs_rq->leaf_cfs_rq_list, rq->tmp_alone_branch);
/*
* update tmp_alone_branch to points to the new begin
* of the branch
*/
rq->tmp_alone_branch = &cfs_rq->leaf_cfs_rq_list;
return false;
}
static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
if (cfs_rq->on_list) {
struct rq *rq = rq_of(cfs_rq);
/*
* With cfs_rq being unthrottled/throttled during an enqueue,
* it can happen the tmp_alone_branch points the a leaf that
* we finally want to del. In this case, tmp_alone_branch moves
* to the prev element but it will point to rq->leaf_cfs_rq_list
* at the end of the enqueue.
*/
if (rq->tmp_alone_branch == &cfs_rq->leaf_cfs_rq_list)
rq->tmp_alone_branch = cfs_rq->leaf_cfs_rq_list.prev;
list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
cfs_rq->on_list = 0;
}
}
static inline void assert_list_leaf_cfs_rq(struct rq *rq)
{
SCHED_WARN_ON(rq->tmp_alone_branch != &rq->leaf_cfs_rq_list);
}
/* Iterate thr' all leaf cfs_rq's on a runqueue */
#define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \
list_for_each_entry_safe(cfs_rq, pos, &rq->leaf_cfs_rq_list, \
leaf_cfs_rq_list)
/* Do the two (enqueued) entities belong to the same group ? */
static inline struct cfs_rq *
is_same_group(struct sched_entity *se, struct sched_entity *pse)
{
if (se->cfs_rq == pse->cfs_rq)
return se->cfs_rq;
return NULL;
}
static inline struct sched_entity *parent_entity(const struct sched_entity *se)
{
return se->parent;
}
static void
find_matching_se(struct sched_entity **se, struct sched_entity **pse)
{
int se_depth, pse_depth;
/*
* preemption test can be made between sibling entities who are in the
* same cfs_rq i.e who have a common parent. Walk up the hierarchy of
* both tasks until we find their ancestors who are siblings of common
* parent.
*/
/* First walk up until both entities are at same depth */
se_depth = (*se)->depth;
pse_depth = (*pse)->depth;
while (se_depth > pse_depth) {
se_depth--;
*se = parent_entity(*se);
}
while (pse_depth > se_depth) {
pse_depth--;
*pse = parent_entity(*pse);
}
while (!is_same_group(*se, *pse)) {
*se = parent_entity(*se);
*pse = parent_entity(*pse);
}
}
static int tg_is_idle(struct task_group *tg)
{
return tg->idle > 0;
}
static int cfs_rq_is_idle(struct cfs_rq *cfs_rq)
{
return cfs_rq->idle > 0;
}
static int se_is_idle(struct sched_entity *se)
{
if (entity_is_task(se))
return task_has_idle_policy(task_of(se));
return cfs_rq_is_idle(group_cfs_rq(se));
}
#else /* !CONFIG_FAIR_GROUP_SCHED */
#define for_each_sched_entity(se) \
for (; se; se = NULL)
static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
return true;
}
static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
}
static inline void assert_list_leaf_cfs_rq(struct rq *rq)
{
}
#define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \
for (cfs_rq = &rq->cfs, pos = NULL; cfs_rq; cfs_rq = pos)
static inline struct sched_entity *parent_entity(struct sched_entity *se)
{
return NULL;
}
static inline void
find_matching_se(struct sched_entity **se, struct sched_entity **pse)
{
}
static inline int tg_is_idle(struct task_group *tg)
{
return 0;
}
static int cfs_rq_is_idle(struct cfs_rq *cfs_rq)
{
return 0;
}
static int se_is_idle(struct sched_entity *se)
{
return 0;
}
#endif /* CONFIG_FAIR_GROUP_SCHED */
static __always_inline
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
/**************************************************************
* Scheduling class tree data structure manipulation methods:
*/
static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
{
s64 delta = (s64)(vruntime - max_vruntime);
if (delta > 0)
max_vruntime = vruntime;
return max_vruntime;
}
static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
{
s64 delta = (s64)(vruntime - min_vruntime);
if (delta < 0)
min_vruntime = vruntime;
return min_vruntime;
}
static inline bool entity_before(const struct sched_entity *a,
const struct sched_entity *b)
{
return (s64)(a->vruntime - b->vruntime) < 0;
}
#define __node_2_se(node) \
rb_entry((node), struct sched_entity, run_node)
static void update_min_vruntime(struct cfs_rq *cfs_rq)
{
struct sched_entity *curr = cfs_rq->curr;
struct rb_node *leftmost = rb_first_cached(&cfs_rq->tasks_timeline);
u64 vruntime = cfs_rq->min_vruntime;
if (curr) {
if (curr->on_rq)
vruntime = curr->vruntime;
else
curr = NULL;
}
if (leftmost) { /* non-empty tree */
struct sched_entity *se = __node_2_se(leftmost);
if (!curr)
vruntime = se->vruntime;
else
vruntime = min_vruntime(vruntime, se->vruntime);
}
/* ensure we never gain time by being placed backwards. */
u64_u32_store(cfs_rq->min_vruntime,
max_vruntime(cfs_rq->min_vruntime, vruntime));
}
static inline bool __entity_less(struct rb_node *a, const struct rb_node *b)
{
return entity_before(__node_2_se(a), __node_2_se(b));
}
/*
* Enqueue an entity into the rb-tree:
*/
static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
rb_add_cached(&se->run_node, &cfs_rq->tasks_timeline, __entity_less);
}
static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
rb_erase_cached(&se->run_node, &cfs_rq->tasks_timeline);
}
struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
{
struct rb_node *left = rb_first_cached(&cfs_rq->tasks_timeline);
if (!left)
return NULL;
return __node_2_se(left);
}
static struct sched_entity *__pick_next_entity(struct sched_entity *se)
{
struct rb_node *next = rb_next(&se->run_node);
if (!next)
return NULL;
return __node_2_se(next);
}
#ifdef CONFIG_SCHED_DEBUG
struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
{
struct rb_node *last = rb_last(&cfs_rq->tasks_timeline.rb_root);
if (!last)
return NULL;
return __node_2_se(last);
}
/**************************************************************
* Scheduling class statistics methods:
*/
int sched_update_scaling(void)
{
unsigned int factor = get_update_sysctl_factor();
sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
sysctl_sched_min_granularity);
#define WRT_SYSCTL(name) \
(normalized_sysctl_##name = sysctl_##name / (factor))
WRT_SYSCTL(sched_min_granularity);
WRT_SYSCTL(sched_latency);
WRT_SYSCTL(sched_wakeup_granularity);
#undef WRT_SYSCTL
return 0;
}
#endif
/*
* delta /= w
*/
static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
{
if (unlikely(se->load.weight != NICE_0_LOAD))
delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
return delta;
}
/*
* The idea is to set a period in which each task runs once.
*
* When there are too many tasks (sched_nr_latency) we have to stretch
* this period because otherwise the slices get too small.
*
* p = (nr <= nl) ? l : l*nr/nl
*/
static u64 __sched_period(unsigned long nr_running)
{
if (unlikely(nr_running > sched_nr_latency))
return nr_running * sysctl_sched_min_granularity;
else
return sysctl_sched_latency;
}
static bool sched_idle_cfs_rq(struct cfs_rq *cfs_rq);
/*
* We calculate the wall-time slice from the period by taking a part
* proportional to the weight.
*
* s = p*P[w/rw]
*/
static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
unsigned int nr_running = cfs_rq->nr_running;
struct sched_entity *init_se = se;
unsigned int min_gran;
u64 slice;
if (sched_feat(ALT_PERIOD))
nr_running = rq_of(cfs_rq)->cfs.h_nr_running;
slice = __sched_period(nr_running + !se->on_rq);
for_each_sched_entity(se) {
struct load_weight *load;
struct load_weight lw;
struct cfs_rq *qcfs_rq;
qcfs_rq = cfs_rq_of(se);
load = &qcfs_rq->load;
if (unlikely(!se->on_rq)) {
lw = qcfs_rq->load;
update_load_add(&lw, se->load.weight);
load = &lw;
}
slice = __calc_delta(slice, se->load.weight, load);
}
if (sched_feat(BASE_SLICE)) {
if (se_is_idle(init_se) && !sched_idle_cfs_rq(cfs_rq))
min_gran = sysctl_sched_idle_min_granularity;
else
min_gran = sysctl_sched_min_granularity;
slice = max_t(u64, slice, min_gran);
}
return slice;
}
/*
* We calculate the vruntime slice of a to-be-inserted task.
*
* vs = s/w
*/
static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
return calc_delta_fair(sched_slice(cfs_rq, se), se);
}
#include "pelt.h"
#ifdef CONFIG_SMP
static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu);
static unsigned long task_h_load(struct task_struct *p);
static unsigned long capacity_of(int cpu);
/* Give new sched_entity start runnable values to heavy its load in infant time */
void init_entity_runnable_average(struct sched_entity *se)
{
struct sched_avg *sa = &se->avg;
memset(sa, 0, sizeof(*sa));
/*
* Tasks are initialized with full load to be seen as heavy tasks until
* they get a chance to stabilize to their real load level.
* Group entities are initialized with zero load to reflect the fact that
* nothing has been attached to the task group yet.
*/
if (entity_is_task(se))
sa->load_avg = scale_load_down(se->load.weight);
/* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
}
/*
* With new tasks being created, their initial util_avgs are extrapolated
* based on the cfs_rq's current util_avg:
*
* util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
*
* However, in many cases, the above util_avg does not give a desired
* value. Moreover, the sum of the util_avgs may be divergent, such
* as when the series is a harmonic series.
*
* To solve this problem, we also cap the util_avg of successive tasks to
* only 1/2 of the left utilization budget:
*
* util_avg_cap = (cpu_scale - cfs_rq->avg.util_avg) / 2^n
*
* where n denotes the nth task and cpu_scale the CPU capacity.
*
* For example, for a CPU with 1024 of capacity, a simplest series from
* the beginning would be like:
*
* task util_avg: 512, 256, 128, 64, 32, 16, 8, ...
* cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
*
* Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
* if util_avg > util_avg_cap.
*/
void post_init_entity_util_avg(struct task_struct *p)
{
struct sched_entity *se = &p->se;
struct cfs_rq *cfs_rq = cfs_rq_of(se);
struct sched_avg *sa = &se->avg;
long cpu_scale = arch_scale_cpu_capacity(cpu_of(rq_of(cfs_rq)));
long cap = (long)(cpu_scale - cfs_rq->avg.util_avg) / 2;
if (p->sched_class != &fair_sched_class) {
/*
* For !fair tasks do:
*
update_cfs_rq_load_avg(now, cfs_rq);
attach_entity_load_avg(cfs_rq, se);
switched_from_fair(rq, p);
*
* such that the next switched_to_fair() has the
* expected state.
*/
se->avg.last_update_time = cfs_rq_clock_pelt(cfs_rq);
return;
}
if (cap > 0) {
if (cfs_rq->avg.util_avg != 0) {
sa->util_avg = cfs_rq->avg.util_avg * se->load.weight;
sa->util_avg /= (cfs_rq->avg.load_avg + 1);
if (sa->util_avg > cap)
sa->util_avg = cap;
} else {
sa->util_avg = cap;
}
}
sa->runnable_avg = sa->util_avg;
}
#else /* !CONFIG_SMP */
void init_entity_runnable_average(struct sched_entity *se)
{
}
void post_init_entity_util_avg(struct task_struct *p)
{
}
static void update_tg_load_avg(struct cfs_rq *cfs_rq)
{
}
#endif /* CONFIG_SMP */
/*
* Update the current task's runtime statistics.
*/
static void update_curr(struct cfs_rq *cfs_rq)
{
struct sched_entity *curr = cfs_rq->curr;
u64 now = rq_clock_task(rq_of(cfs_rq));
u64 delta_exec;
if (unlikely(!curr))
return;
delta_exec = now - curr->exec_start;
if (unlikely((s64)delta_exec <= 0))
return;
curr->exec_start = now;
if (schedstat_enabled()) {
struct sched_statistics *stats;
stats = __schedstats_from_se(curr);
__schedstat_set(stats->exec_max,
max(delta_exec, stats->exec_max));
}
curr->sum_exec_runtime += delta_exec;
schedstat_add(cfs_rq->exec_clock, delta_exec);
curr->vruntime += calc_delta_fair(delta_exec, curr);
update_min_vruntime(cfs_rq);
if (entity_is_task(curr)) {
struct task_struct *curtask = task_of(curr);
trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
cgroup_account_cputime(curtask, delta_exec);
account_group_exec_runtime(curtask, delta_exec);
}
account_cfs_rq_runtime(cfs_rq, delta_exec);
}
static void update_curr_fair(struct rq *rq)
{
update_curr(cfs_rq_of(&rq->curr->se));
}
static inline void
update_stats_wait_start_fair(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
struct sched_statistics *stats;
struct task_struct *p = NULL;
if (!schedstat_enabled())
return;
stats = __schedstats_from_se(se);
if (entity_is_task(se))
p = task_of(se);
__update_stats_wait_start(rq_of(cfs_rq), p, stats);
}
static inline void
update_stats_wait_end_fair(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
struct sched_statistics *stats;
struct task_struct *p = NULL;
if (!schedstat_enabled())
return;
stats = __schedstats_from_se(se);
/*
* When the sched_schedstat changes from 0 to 1, some sched se
* maybe already in the runqueue, the se->statistics.wait_start
* will be 0.So it will let the delta wrong. We need to avoid this
* scenario.
*/
if (unlikely(!schedstat_val(stats->wait_start)))
return;
if (entity_is_task(se))
p = task_of(se);
__update_stats_wait_end(rq_of(cfs_rq), p, stats);
}
static inline void
update_stats_enqueue_sleeper_fair(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
struct sched_statistics *stats;
struct task_struct *tsk = NULL;
if (!schedstat_enabled())
return;
stats = __schedstats_from_se(se);
if (entity_is_task(se))
tsk = task_of(se);
__update_stats_enqueue_sleeper(rq_of(cfs_rq), tsk, stats);
}
/*
* Task is being enqueued - update stats:
*/
static inline void
update_stats_enqueue_fair(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
if (!schedstat_enabled())
return;
/*
* Are we enqueueing a waiting task? (for current tasks
* a dequeue/enqueue event is a NOP)
*/
if (se != cfs_rq->curr)
update_stats_wait_start_fair(cfs_rq, se);
if (flags & ENQUEUE_WAKEUP)
update_stats_enqueue_sleeper_fair(cfs_rq, se);
}
static inline void
update_stats_dequeue_fair(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
if (!schedstat_enabled())
return;
/*
* Mark the end of the wait period if dequeueing a
* waiting task:
*/
if (se != cfs_rq->curr)
update_stats_wait_end_fair(cfs_rq, se);
if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) {
struct task_struct *tsk = task_of(se);
unsigned int state;
/* XXX racy against TTWU */
state = READ_ONCE(tsk->__state);
if (state & TASK_INTERRUPTIBLE)
__schedstat_set(tsk->stats.sleep_start,
rq_clock(rq_of(cfs_rq)));
if (state & TASK_UNINTERRUPTIBLE)
__schedstat_set(tsk->stats.block_start,
rq_clock(rq_of(cfs_rq)));
}
}
/*
* We are picking a new current task - update its stats:
*/
static inline void
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
/*
* We are starting a new run period:
*/
se->exec_start = rq_clock_task(rq_of(cfs_rq));
}
/**************************************************
* Scheduling class queueing methods:
*/
static inline bool is_core_idle(int cpu)
{
#ifdef CONFIG_SCHED_SMT
int sibling;
for_each_cpu(sibling, cpu_smt_mask(cpu)) {
if (cpu == sibling)
continue;
if (!idle_cpu(sibling))
return false;
}
#endif
return true;
}
#ifdef CONFIG_NUMA
#define NUMA_IMBALANCE_MIN 2
static inline long
adjust_numa_imbalance(int imbalance, int dst_running, int imb_numa_nr)
{
/*
* Allow a NUMA imbalance if busy CPUs is less than the maximum
* threshold. Above this threshold, individual tasks may be contending
* for both memory bandwidth and any shared HT resources. This is an
* approximation as the number of running tasks may not be related to
* the number of busy CPUs due to sched_setaffinity.
*/
if (dst_running > imb_numa_nr)
return imbalance;
/*
* Allow a small imbalance based on a simple pair of communicating
* tasks that remain local when the destination is lightly loaded.
*/
if (imbalance <= NUMA_IMBALANCE_MIN)
return 0;
return imbalance;
}
#endif /* CONFIG_NUMA */
#ifdef CONFIG_NUMA_BALANCING
/*
* Approximate time to scan a full NUMA task in ms. The task scan period is
* calculated based on the tasks virtual memory size and
* numa_balancing_scan_size.
*/
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;
/* The page with hint page fault latency < threshold in ms is considered hot */
unsigned int sysctl_numa_balancing_hot_threshold = MSEC_PER_SEC;
struct numa_group {
refcount_t refcount;
spinlock_t lock; /* nr_tasks, tasks */
int nr_tasks;
pid_t gid;
int active_nodes;
struct rcu_head rcu;
unsigned long total_faults;
unsigned long max_faults_cpu;
/*
* faults[] array is split into two regions: faults_mem and faults_cpu.
*
* Faults_cpu is used to decide whether memory should move
* towards the CPU. As a consequence, these stats are weighted
* more by CPU use than by memory faults.
*/
unsigned long faults[];
};
/*
* For functions that can be called in multiple contexts that permit reading
* ->numa_group (see struct task_struct for locking rules).
*/
static struct numa_group *deref_task_numa_group(struct task_struct *p)
{
return rcu_dereference_check(p->numa_group, p == current ||
(lockdep_is_held(__rq_lockp(task_rq(p))) && !READ_ONCE(p->on_cpu)));
}
static struct numa_group *deref_curr_numa_group(struct task_struct *p)
{
return rcu_dereference_protected(p->numa_group, p == current);
}
static inline unsigned long group_faults_priv(struct numa_group *ng);
static inline unsigned long group_faults_shared(struct numa_group *ng);
static unsigned int task_nr_scan_windows(struct task_struct *p)
{
unsigned long rss = 0;
unsigned long nr_scan_pages;
/*
* Calculations based on RSS as non-present and empty pages are skipped
* by the PTE scanner and NUMA hinting faults should be trapped based
* on resident pages
*/
nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
rss = get_mm_rss(p->mm);
if (!rss)
rss = nr_scan_pages;
rss = round_up(rss, nr_scan_pages);
return rss / nr_scan_pages;
}
/* For sanity's sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
#define MAX_SCAN_WINDOW 2560
static unsigned int task_scan_min(struct task_struct *p)
{
unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
unsigned int scan, floor;
unsigned int windows = 1;
if (scan_size < MAX_SCAN_WINDOW)
windows = MAX_SCAN_WINDOW / scan_size;
floor = 1000 / windows;
scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
return max_t(unsigned int, floor, scan);
}
static unsigned int task_scan_start(struct task_struct *p)
{
unsigned long smin = task_scan_min(p);
unsigned long period = smin;
struct numa_group *ng;
/* Scale the maximum scan period with the amount of shared memory. */
rcu_read_lock();
ng = rcu_dereference(p->numa_group);
if (ng) {
unsigned long shared = group_faults_shared(ng);
unsigned long private = group_faults_priv(ng);
period *= refcount_read(&ng->refcount);
period *= shared + 1;
period /= private + shared + 1;
}
rcu_read_unlock();
return max(smin, period);
}
static unsigned int task_scan_max(struct task_struct *p)
{
unsigned long smin = task_scan_min(p);
unsigned long smax;
struct numa_group *ng;
/* Watch for min being lower than max due to floor calculations */
smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
/* Scale the maximum scan period with the amount of shared memory. */
ng = deref_curr_numa_group(p);
if (ng) {
unsigned long shared = group_faults_shared(ng);
unsigned long private = group_faults_priv(ng);
unsigned long period = smax;
period *= refcount_read(&ng->refcount);
period *= shared + 1;
period /= private + shared + 1;
smax = max(smax, period);
}
return max(smin, smax);
}
static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
{
rq->nr_numa_running += (p->numa_preferred_nid != NUMA_NO_NODE);
rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
}
static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
{
rq->nr_numa_running -= (p->numa_preferred_nid != NUMA_NO_NODE);
rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
}
/* Shared or private faults. */
#define NR_NUMA_HINT_FAULT_TYPES 2
/* Memory and CPU locality */
#define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
/* Averaged statistics, and temporary buffers. */
#define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
pid_t task_numa_group_id(struct task_struct *p)
{
struct numa_group *ng;
pid_t gid = 0;
rcu_read_lock();
ng = rcu_dereference(p->numa_group);
if (ng)
gid = ng->gid;
rcu_read_unlock();
return gid;
}
/*
* The averaged statistics, shared & private, memory & CPU,
* occupy the first half of the array. The second half of the
* array is for current counters, which are averaged into the
* first set by task_numa_placement.
*/
static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
{
return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
}
static inline unsigned long task_faults(struct task_struct *p, int nid)
{
if (!p->numa_faults)
return 0;
return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
}
static inline unsigned long group_faults(struct task_struct *p, int nid)
{
struct numa_group *ng = deref_task_numa_group(p);
if (!ng)
return 0;
return ng->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
ng->faults[task_faults_idx(NUMA_MEM, nid, 1)];
}
static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
{
return group->faults[task_faults_idx(NUMA_CPU, nid, 0)] +
group->faults[task_faults_idx(NUMA_CPU, nid, 1)];
}
static inline unsigned long group_faults_priv(struct numa_group *ng)
{
unsigned long faults = 0;
int node;
for_each_online_node(node) {
faults += ng->faults[task_faults_idx(NUMA_MEM, node, 1)];
}
return faults;
}
static inline unsigned long group_faults_shared(struct numa_group *ng)
{
unsigned long faults = 0;
int node;
for_each_online_node(node) {
faults += ng->faults[task_faults_idx(NUMA_MEM, node, 0)];
}
return faults;
}
/*
* A node triggering more than 1/3 as many NUMA faults as the maximum is
* considered part of a numa group's pseudo-interleaving set. Migrations
* between these nodes are slowed down, to allow things to settle down.
*/
#define ACTIVE_NODE_FRACTION 3
static bool numa_is_active_node(int nid, struct numa_group *ng)
{
return group_faults_cpu(ng, nid) * ACTIVE_NODE_FRACTION > ng->max_faults_cpu;
}
/* Handle placement on systems where not all nodes are directly connected. */
static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
int lim_dist, bool task)
{
unsigned long score = 0;
int node, max_dist;
/*
* All nodes are directly connected, and the same distance
* from each other. No need for fancy placement algorithms.
*/
if (sched_numa_topology_type == NUMA_DIRECT)
return 0;
/* sched_max_numa_distance may be changed in parallel. */
max_dist = READ_ONCE(sched_max_numa_distance);
/*
* This code is called for each node, introducing N^2 complexity,
* which should be ok given the number of nodes rarely exceeds 8.
*/
for_each_online_node(node) {
unsigned long faults;
int dist = node_distance(nid, node);
/*
* The furthest away nodes in the system are not interesting
* for placement; nid was already counted.
*/
if (dist >= max_dist || node == nid)
continue;
/*
* On systems with a backplane NUMA topology, compare groups
* of nodes, and move tasks towards the group with the most
* memory accesses. When comparing two nodes at distance
* "hoplimit", only nodes closer by than "hoplimit" are part
* of each group. Skip other nodes.
*/
if (sched_numa_topology_type == NUMA_BACKPLANE && dist >= lim_dist)
continue;
/* Add up the faults from nearby nodes. */
if (task)
faults = task_faults(p, node);
else
faults = group_faults(p, node);
/*
* On systems with a glueless mesh NUMA topology, there are
* no fixed "groups of nodes". Instead, nodes that are not
* directly connected bounce traffic through intermediate
* nodes; a numa_group can occupy any set of nodes.
* The further away a node is, the less the faults count.
* This seems to result in good task placement.
*/
if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
faults *= (max_dist - dist);
faults /= (max_dist - LOCAL_DISTANCE);
}
score += faults;
}
return score;
}
/*
* These return the fraction of accesses done by a particular task, or
* task group, on a particular numa node. The group weight is given a
* larger multiplier, in order to group tasks together that are almost
* evenly spread out between numa nodes.
*/
static inline unsigned long task_weight(struct task_struct *p, int nid,
int dist)
{
unsigned long faults, total_faults;
if (!p->numa_faults)
return 0;
total_faults = p->total_numa_faults;
if (!total_faults)
return 0;
faults = task_faults(p, nid);
faults += score_nearby_nodes(p, nid, dist, true);
return 1000 * faults / total_faults;
}
static inline unsigned long group_weight(struct task_struct *p, int nid,
int dist)
{
struct numa_group *ng = deref_task_numa_group(p);
unsigned long faults, total_faults;
if (!ng)
return 0;
total_faults = ng->total_faults;
if (!total_faults)
return 0;
faults = group_faults(p, nid);
faults += score_nearby_nodes(p, nid, dist, false);
return 1000 * faults / total_faults;
}
/*
* If memory tiering mode is enabled, cpupid of slow memory page is
* used to record scan time instead of CPU and PID. When tiering mode
* is disabled at run time, the scan time (in cpupid) will be
* interpreted as CPU and PID. So CPU needs to be checked to avoid to
* access out of array bound.
*/
static inline bool cpupid_valid(int cpupid)
{
return cpupid_to_cpu(cpupid) < nr_cpu_ids;
}
/*
* For memory tiering mode, if there are enough free pages (more than
* enough watermark defined here) in fast memory node, to take full
* advantage of fast memory capacity, all recently accessed slow
* memory pages will be migrated to fast memory node without
* considering hot threshold.
*/
static bool pgdat_free_space_enough(struct pglist_data *pgdat)
{
int z;
unsigned long enough_wmark;
enough_wmark = max(1UL * 1024 * 1024 * 1024 >> PAGE_SHIFT,
pgdat->node_present_pages >> 4);
for (z = pgdat->nr_zones - 1; z >= 0; z--) {
struct zone *zone = pgdat->node_zones + z;
if (!populated_zone(zone))
continue;
if (zone_watermark_ok(zone, 0,
wmark_pages(zone, WMARK_PROMO) + enough_wmark,
ZONE_MOVABLE, 0))
return true;
}
return false;
}
/*
* For memory tiering mode, when page tables are scanned, the scan
* time will be recorded in struct page in addition to make page
* PROT_NONE for slow memory page. So when the page is accessed, in
* hint page fault handler, the hint page fault latency is calculated
* via,
*
* hint page fault latency = hint page fault time - scan time
*
* The smaller the hint page fault latency, the higher the possibility
* for the page to be hot.
*/
static int numa_hint_fault_latency(struct page *page)
{
int last_time, time;
time = jiffies_to_msecs(jiffies);
last_time = xchg_page_access_time(page, time);
return (time - last_time) & PAGE_ACCESS_TIME_MASK;
}
/*
* For memory tiering mode, too high promotion/demotion throughput may
* hurt application latency. So we provide a mechanism to rate limit
* the number of pages that are tried to be promoted.
*/
static bool numa_promotion_rate_limit(struct pglist_data *pgdat,
unsigned long rate_limit, int nr)
{
unsigned long nr_cand;
unsigned int now, start;
now = jiffies_to_msecs(jiffies);
mod_node_page_state(pgdat, PGPROMOTE_CANDIDATE, nr);
nr_cand = node_page_state(pgdat, PGPROMOTE_CANDIDATE);
start = pgdat->nbp_rl_start;
if (now - start > MSEC_PER_SEC &&
cmpxchg(&pgdat->nbp_rl_start, start, now) == start)
pgdat->nbp_rl_nr_cand = nr_cand;
if (nr_cand - pgdat->nbp_rl_nr_cand >= rate_limit)
return true;
return false;
}
#define NUMA_MIGRATION_ADJUST_STEPS 16
static void numa_promotion_adjust_threshold(struct pglist_data *pgdat,
unsigned long rate_limit,
unsigned int ref_th)
{
unsigned int now, start, th_period, unit_th, th;
unsigned long nr_cand, ref_cand, diff_cand;
now = jiffies_to_msecs(jiffies);
th_period = sysctl_numa_balancing_scan_period_max;
start = pgdat->nbp_th_start;
if (now - start > th_period &&
cmpxchg(&pgdat->nbp_th_start, start, now) == start) {
ref_cand = rate_limit *
sysctl_numa_balancing_scan_period_max / MSEC_PER_SEC;
nr_cand = node_page_state(pgdat, PGPROMOTE_CANDIDATE);
diff_cand = nr_cand - pgdat->nbp_th_nr_cand;
unit_th = ref_th * 2 / NUMA_MIGRATION_ADJUST_STEPS;
th = pgdat->nbp_threshold ? : ref_th;
if (diff_cand > ref_cand * 11 / 10)
th = max(th - unit_th, unit_th);
else if (diff_cand < ref_cand * 9 / 10)
th = min(th + unit_th, ref_th * 2);
pgdat->nbp_th_nr_cand = nr_cand;
pgdat->nbp_threshold = th;
}
}
bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
int src_nid, int dst_cpu)
{
struct numa_group *ng = deref_curr_numa_group(p);
int dst_nid = cpu_to_node(dst_cpu);
int last_cpupid, this_cpupid;
/*
* The pages in slow memory node should be migrated according
* to hot/cold instead of private/shared.
*/
if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING &&
!node_is_toptier(src_nid)) {
struct pglist_data *pgdat;
unsigned long rate_limit;
unsigned int latency, th, def_th;
pgdat = NODE_DATA(dst_nid);
if (pgdat_free_space_enough(pgdat)) {
/* workload changed, reset hot threshold */
pgdat->nbp_threshold = 0;
return true;
}
def_th = sysctl_numa_balancing_hot_threshold;
rate_limit = sysctl_numa_balancing_promote_rate_limit << \
(20 - PAGE_SHIFT);
numa_promotion_adjust_threshold(pgdat, rate_limit, def_th);
th = pgdat->nbp_threshold ? : def_th;
latency = numa_hint_fault_latency(page);
if (latency >= th)
return false;
return !numa_promotion_rate_limit(pgdat, rate_limit,
thp_nr_pages(page));
}
this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) &&
!node_is_toptier(src_nid) && !cpupid_valid(last_cpupid))
return false;
/*
* Allow first faults or private faults to migrate immediately early in
* the lifetime of a task. The magic number 4 is based on waiting for
* two full passes of the "multi-stage node selection" test that is
* executed below.
*/
if ((p->numa_preferred_nid == NUMA_NO_NODE || p->numa_scan_seq <= 4) &&
(cpupid_pid_unset(last_cpupid) || cpupid_match_pid(p, last_cpupid)))
return true;
/*
* Multi-stage node selection is used in conjunction with a periodic
* migration fault to build a temporal task<->page relation. By using
* a two-stage filter we remove short/unlikely relations.
*
* Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
* a task's usage of a particular page (n_p) per total usage of this
* page (n_t) (in a given time-span) to a probability.
*
* Our periodic faults will sample this probability and getting the
* same result twice in a row, given these samples are fully
* independent, is then given by P(n)^2, provided our sample period
* is sufficiently short compared to the usage pattern.
*
* This quadric squishes small probabilities, making it less likely we
* act on an unlikely task<->page relation.
*/
if (!cpupid_pid_unset(last_cpupid) &&
cpupid_to_nid(last_cpupid) != dst_nid)
return false;
/* Always allow migrate on private faults */
if (cpupid_match_pid(p, last_cpupid))
return true;
/* A shared fault, but p->numa_group has not been set up yet. */
if (!ng)
return true;
/*
* Destination node is much more heavily used than the source
* node? Allow migration.
*/
if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
ACTIVE_NODE_FRACTION)
return true;
/*
* Distribute memory according to CPU & memory use on each node,
* with 3/4 hysteresis to avoid unnecessary memory migrations:
*
* faults_cpu(dst) 3 faults_cpu(src)
* --------------- * - > ---------------
* faults_mem(dst) 4 faults_mem(src)
*/
return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * 3 >
group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4;
}
/*
* 'numa_type' describes the node at the moment of load balancing.
*/
enum numa_type {
/* The node has spare capacity that can be used to run more tasks. */
node_has_spare = 0,
/*
* The node is fully used and the tasks don't compete for more CPU
* cycles. Nevertheless, some tasks might wait before running.
*/
node_fully_busy,
/*
* The node is overloaded and can't provide expected CPU cycles to all
* tasks.
*/
node_overloaded
};
/* Cached statistics for all CPUs within a node */
struct numa_stats {
unsigned long load;
unsigned long runnable;
unsigned long util;
/* Total compute capacity of CPUs on a node */
unsigned long compute_capacity;
unsigned int nr_running;
unsigned int weight;
enum numa_type node_type;
int idle_cpu;
};
struct task_numa_env {
struct task_struct *p;
int src_cpu, src_nid;
int dst_cpu, dst_nid;
int imb_numa_nr;
struct numa_stats src_stats, dst_stats;
int imbalance_pct;
int dist;
struct task_struct *best_task;
long best_imp;
int best_cpu;
};
static unsigned long cpu_load(struct rq *rq);
static unsigned long cpu_runnable(struct rq *rq);
static inline enum
numa_type numa_classify(unsigned int imbalance_pct,
struct numa_stats *ns)
{
if ((ns->nr_running > ns->weight) &&
(((ns->compute_capacity * 100) < (ns->util * imbalance_pct)) ||
((ns->compute_capacity * imbalance_pct) < (ns->runnable * 100))))
return node_overloaded;
if ((ns->nr_running < ns->weight) ||
(((ns->compute_capacity * 100) > (ns->util * imbalance_pct)) &&
((ns->compute_capacity * imbalance_pct) > (ns->runnable * 100))))
return node_has_spare;
return node_fully_busy;
}
#ifdef CONFIG_SCHED_SMT
/* Forward declarations of select_idle_sibling helpers */
static inline bool test_idle_cores(int cpu);
static inline int numa_idle_core(int idle_core, int cpu)
{
if (!static_branch_likely(&sched_smt_present) ||
idle_core >= 0 || !test_idle_cores(cpu))
return idle_core;
/*
* Prefer cores instead of packing HT siblings
* and triggering future load balancing.
*/
if (is_core_idle(cpu))
idle_core = cpu;
return idle_core;
}
#else
static inline int numa_idle_core(int idle_core, int cpu)
{
return idle_core;
}
#endif
/*
* Gather all necessary information to make NUMA balancing placement
* decisions that are compatible with standard load balancer. This
* borrows code and logic from update_sg_lb_stats but sharing a
* common implementation is impractical.
*/
static void update_numa_stats(struct task_numa_env *env,
struct numa_stats *ns, int nid,
bool find_idle)
{
int cpu, idle_core = -1;
memset(ns, 0, sizeof(*ns));
ns->idle_cpu = -1;
rcu_read_lock();
for_each_cpu(cpu, cpumask_of_node(nid)) {
struct rq *rq = cpu_rq(cpu);
ns->load += cpu_load(rq);
ns->runnable += cpu_runnable(rq);
ns->util += cpu_util_cfs(cpu);
ns->nr_running += rq->cfs.h_nr_running;
ns->compute_capacity += capacity_of(cpu);
if (find_idle && idle_core < 0 && !rq->nr_running && idle_cpu(cpu)) {
if (READ_ONCE(rq->numa_migrate_on) ||
!cpumask_test_cpu(cpu, env->p->cpus_ptr))
continue;
if (ns->idle_cpu == -1)
ns->idle_cpu = cpu;
idle_core = numa_idle_core(idle_core, cpu);
}
}
rcu_read_unlock();
ns->weight = cpumask_weight(cpumask_of_node(nid));
ns->node_type = numa_classify(env->imbalance_pct, ns);
if (idle_core >= 0)
ns->idle_cpu = idle_core;
}
static void task_numa_assign(struct task_numa_env *env,
struct task_struct *p, long imp)
{
struct rq *rq = cpu_rq(env->dst_cpu);
/* Check if run-queue part of active NUMA balance. */
if (env->best_cpu != env->dst_cpu && xchg(&rq->numa_migrate_on, 1)) {
int cpu;
int start = env->dst_cpu;
/* Find alternative idle CPU. */
for_each_cpu_wrap(cpu, cpumask_of_node(env->dst_nid), start + 1) {
if (cpu == env->best_cpu || !idle_cpu(cpu) ||
!cpumask_test_cpu(cpu, env->p->cpus_ptr)) {
continue;
}
env->dst_cpu = cpu;
rq = cpu_rq(env->dst_cpu);
if (!xchg(&rq->numa_migrate_on, 1))
goto assign;
}
/* Failed to find an alternative idle CPU */
return;
}
assign:
/*
* Clear previous best_cpu/rq numa-migrate flag, since task now
* found a better CPU to move/swap.
*/
if (env->best_cpu != -1 && env->best_cpu != env->dst_cpu) {
rq = cpu_rq(env->best_cpu);
WRITE_ONCE(rq->numa_migrate_on, 0);
}
if (env->best_task)
put_task_struct(env->best_task);
if (p)
get_task_struct(p);
env->best_task = p;
env->best_imp = imp;
env->best_cpu = env->dst_cpu;
}
static bool load_too_imbalanced(long src_load, long dst_load,
struct task_numa_env *env)
{
long imb, old_imb;
long orig_src_load, orig_dst_load;
long src_capacity, dst_capacity;
/*
* The load is corrected for the CPU capacity available on each node.
*
* src_load dst_load
* ------------ vs ---------
* src_capacity dst_capacity
*/
src_capacity = env->src_stats.compute_capacity;
dst_capacity = env->dst_stats.compute_capacity;
imb = abs(dst_load * src_capacity - src_load * dst_capacity);
orig_src_load = env->src_stats.load;
orig_dst_load = env->dst_stats.load;
old_imb = abs(orig_dst_load * src_capacity - orig_src_load * dst_capacity);
/* Would this change make things worse? */
return (imb > old_imb);
}
/*
* Maximum NUMA importance can be 1998 (2*999);
* SMALLIMP @ 30 would be close to 1998/64.
* Used to deter task migration.
*/
#define SMALLIMP 30
/*
* This checks if the overall compute and NUMA accesses of the system would
* be improved if the source tasks was migrated to the target dst_cpu taking
* into account that it might be best if task running on the dst_cpu should
* be exchanged with the source task
*/
static bool task_numa_compare(struct task_numa_env *env,
long taskimp, long groupimp, bool maymove)
{
struct numa_group *cur_ng, *p_ng = deref_curr_numa_group(env->p);
struct rq *dst_rq = cpu_rq(env->dst_cpu);
long imp = p_ng ? groupimp : taskimp;
struct task_struct *cur;
long src_load, dst_load;
int dist = env->dist;
long moveimp = imp;
long load;
bool stopsearch = false;
if (READ_ONCE(dst_rq->numa_migrate_on))
return false;
rcu_read_lock();
cur = rcu_dereference(dst_rq->curr);
if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur)))
cur = NULL;
/*
* Because we have preemption enabled we can get migrated around and
* end try selecting ourselves (current == env->p) as a swap candidate.
*/
if (cur == env->p) {
stopsearch = true;
goto unlock;
}
if (!cur) {
if (maymove && moveimp >= env->best_imp)
goto assign;
else
goto unlock;
}
/* Skip this swap candidate if cannot move to the source cpu. */
if (!cpumask_test_cpu(env->src_cpu, cur->cpus_ptr))
goto unlock;
/*
* Skip this swap candidate if it is not moving to its preferred
* node and the best task is.
*/
if (env->best_task &&
env->best_task->numa_preferred_nid == env->src_nid &&
cur->numa_preferred_nid != env->src_nid) {
goto unlock;
}
/*
* "imp" is the fault differential for the source task between the
* source and destination node. Calculate the total differential for
* the source task and potential destination task. The more negative
* the value is, the more remote accesses that would be expected to
* be incurred if the tasks were swapped.
*
* If dst and source tasks are in the same NUMA group, or not
* in any group then look only at task weights.
*/
cur_ng = rcu_dereference(cur->numa_group);
if (cur_ng == p_ng) {
/*
* Do not swap within a group or between tasks that have
* no group if there is spare capacity. Swapping does
* not address the load imbalance and helps one task at
* the cost of punishing another.
*/
if (env->dst_stats.node_type == node_has_spare)
goto unlock;
imp = taskimp + task_weight(cur, env->src_nid, dist) -
task_weight(cur, env->dst_nid, dist);
/*
* Add some hysteresis to prevent swapping the
* tasks within a group over tiny differences.
*/
if (cur_ng)
imp -= imp / 16;
} else {
/*
* Compare the group weights. If a task is all by itself
* (not part of a group), use the task weight instead.
*/
if (cur_ng && p_ng)
imp += group_weight(cur, env->src_nid, dist) -
group_weight(cur, env->dst_nid, dist);
else
imp += task_weight(cur, env->src_nid, dist) -
task_weight(cur, env->dst_nid, dist);
}
/* Discourage picking a task already on its preferred node */
if (cur->numa_preferred_nid == env->dst_nid)
imp -= imp / 16;
/*
* Encourage picking a task that moves to its preferred node.
* This potentially makes imp larger than it's maximum of
* 1998 (see SMALLIMP and task_weight for why) but in this
* case, it does not matter.
*/
if (cur->numa_preferred_nid == env->src_nid)
imp += imp / 8;
if (maymove && moveimp > imp && moveimp > env->best_imp) {
imp = moveimp;
cur = NULL;
goto assign;
}
/*
* Prefer swapping with a task moving to its preferred node over a
* task that is not.
*/
if (env->best_task && cur->numa_preferred_nid == env->src_nid &&
env->best_task->numa_preferred_nid != env->src_nid) {
goto assign;
}
/*
* If the NUMA importance is less than SMALLIMP,
* task migration might only result in ping pong
* of tasks and also hurt performance due to cache
* misses.
*/
if (imp < SMALLIMP || imp <= env->best_imp + SMALLIMP / 2)
goto unlock;
/*
* In the overloaded case, try and keep the load balanced.
*/
load = task_h_load(env->p) - task_h_load(cur);
if (!load)
goto assign;
dst_load = env->dst_stats.load + load;
src_load = env->src_stats.load - load;
if (load_too_imbalanced(src_load, dst_load, env))
goto unlock;
assign:
/* Evaluate an idle CPU for a task numa move. */
if (!cur) {
int cpu = env->dst_stats.idle_cpu;
/* Nothing cached so current CPU went idle since the search. */
if (cpu < 0)
cpu = env->dst_cpu;
/*
* If the CPU is no longer truly idle and the previous best CPU
* is, keep using it.
*/
if (!idle_cpu(cpu) && env->best_cpu >= 0 &&
idle_cpu(env->best_cpu)) {
cpu = env->best_cpu;
}
env->dst_cpu = cpu;
}
task_numa_assign(env, cur, imp);
/*
* If a move to idle is allowed because there is capacity or load
* balance improves then stop the search. While a better swap
* candidate may exist, a search is not free.
*/
if (maymove && !cur && env->best_cpu >= 0 && idle_cpu(env->best_cpu))
stopsearch = true;
/*
* If a swap candidate must be identified and the current best task
* moves its preferred node then stop the search.
*/
if (!maymove && env->best_task &&
env->best_task->numa_preferred_nid == env->src_nid) {
stopsearch = true;
}
unlock:
rcu_read_unlock();
return stopsearch;
}
static void task_numa_find_cpu(struct task_numa_env *env,
long taskimp, long groupimp)
{
bool maymove = false;
int cpu;
/*
* If dst node has spare capacity, then check if there is an
* imbalance that would be overruled by the load balancer.
*/
if (env->dst_stats.node_type == node_has_spare) {
unsigned int imbalance;
int src_running, dst_running;
/*
* Would movement cause an imbalance? Note that if src has
* more running tasks that the imbalance is ignored as the
* move improves the imbalance from the perspective of the
* CPU load balancer.
* */
src_running = env->src_stats.nr_running - 1;
dst_running = env->dst_stats.nr_running + 1;
imbalance = max(0, dst_running - src_running);
imbalance = adjust_numa_imbalance(imbalance, dst_running,
env->imb_numa_nr);
/* Use idle CPU if there is no imbalance */
if (!imbalance) {
maymove = true;
if (env->dst_stats.idle_cpu >= 0) {
env->dst_cpu = env->dst_stats.idle_cpu;
task_numa_assign(env, NULL, 0);
return;
}
}
} else {
long src_load, dst_load, load;
/*
* If the improvement from just moving env->p direction is better
* than swapping tasks around, check if a move is possible.
*/
load = task_h_load(env->p);
dst_load = env->dst_stats.load + load;
src_load = env->src_stats.load - load;
maymove = !load_too_imbalanced(src_load, dst_load, env);
}
for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
/* Skip this CPU if the source task cannot migrate */
if (!cpumask_test_cpu(cpu, env->p->cpus_ptr))
continue;
env->dst_cpu = cpu;
if (task_numa_compare(env, taskimp, groupimp, maymove))
break;
}
}
static int task_numa_migrate(struct task_struct *p)
{
struct task_numa_env env = {
.p = p,
.src_cpu = task_cpu(p),
.src_nid = task_node(p),
.imbalance_pct = 112,
.best_task = NULL,
.best_imp = 0,
.best_cpu = -1,
};
unsigned long taskweight, groupweight;
struct sched_domain *sd;
long taskimp, groupimp;
struct numa_group *ng;
struct rq *best_rq;
int nid, ret, dist;
/*
* Pick the lowest SD_NUMA domain, as that would have the smallest
* imbalance and would be the first to start moving tasks about.
*
* And we want to avoid any moving of tasks about, as that would create
* random movement of tasks -- counter the numa conditions we're trying
* to satisfy here.
*/
rcu_read_lock();
sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
if (sd) {
env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
env.imb_numa_nr = sd->imb_numa_nr;
}
rcu_read_unlock();
/*
* Cpusets can break the scheduler domain tree into smaller
* balance domains, some of which do not cross NUMA boundaries.
* Tasks that are "trapped" in such domains cannot be migrated
* elsewhere, so there is no point in (re)trying.
*/
if (unlikely(!sd)) {
sched_setnuma(p, task_node(p));
return -EINVAL;
}
env.dst_nid = p->numa_preferred_nid;
dist = env.dist = node_distance(env.src_nid, env.dst_nid);
taskweight = task_weight(p, env.src_nid, dist);
groupweight = group_weight(p, env.src_nid, dist);
update_numa_stats(&env, &env.src_stats, env.src_nid, false);
taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
update_numa_stats(&env, &env.dst_stats, env.dst_nid, true);
/* Try to find a spot on the preferred nid. */
task_numa_find_cpu(&env, taskimp, groupimp);
/*
* Look at other nodes in these cases:
* - there is no space available on the preferred_nid
* - the task is part of a numa_group that is interleaved across
* multiple NUMA nodes; in order to better consolidate the group,
* we need to check other locations.
*/
ng = deref_curr_numa_group(p);
if (env.best_cpu == -1 || (ng && ng->active_nodes > 1)) {
for_each_node_state(nid, N_CPU) {
if (nid == env.src_nid || nid == p->numa_preferred_nid)
continue;
dist = node_distance(env.src_nid, env.dst_nid);
if (sched_numa_topology_type == NUMA_BACKPLANE &&
dist != env.dist) {
taskweight = task_weight(p, env.src_nid, dist);
groupweight = group_weight(p, env.src_nid, dist);
}
/* Only consider nodes where both task and groups benefit */
taskimp = task_weight(p, nid, dist) - taskweight;
groupimp = group_weight(p, nid, dist) - groupweight;
if (taskimp < 0 && groupimp < 0)
continue;
env.dist = dist;
env.dst_nid = nid;
update_numa_stats(&env, &env.dst_stats, env.dst_nid, true);
task_numa_find_cpu(&env, taskimp, groupimp);
}
}
/*
* If the task is part of a workload that spans multiple NUMA nodes,
* and is migrating into one of the workload's active nodes, remember
* this node as the task's preferred numa node, so the workload can
* settle down.
* A task that migrated to a second choice node will be better off
* trying for a better one later. Do not set the preferred node here.
*/
if (ng) {
if (env.best_cpu == -1)
nid = env.src_nid;
else
nid = cpu_to_node(env.best_cpu);
if (nid != p->numa_preferred_nid)
sched_setnuma(p, nid);
}
/* No better CPU than the current one was found. */
if (env.best_cpu == -1) {
trace_sched_stick_numa(p, env.src_cpu, NULL, -1);
return -EAGAIN;
}
best_rq = cpu_rq(env.best_cpu);
if (env.best_task == NULL) {
ret = migrate_task_to(p, env.best_cpu);
WRITE_ONCE(best_rq->numa_migrate_on, 0);
if (ret != 0)
trace_sched_stick_numa(p, env.src_cpu, NULL, env.best_cpu);
return ret;
}
ret = migrate_swap(p, env.best_task, env.best_cpu, env.src_cpu);
WRITE_ONCE(best_rq->numa_migrate_on, 0);
if (ret != 0)
trace_sched_stick_numa(p, env.src_cpu, env.best_task, env.best_cpu);
put_task_struct(env.best_task);
return ret;
}
/* Attempt to migrate a task to a CPU on the preferred node. */
static void numa_migrate_preferred(struct task_struct *p)
{
unsigned long interval = HZ;
/* This task has no NUMA fault statistics yet */
if (unlikely(p->numa_preferred_nid == NUMA_NO_NODE || !p->numa_faults))
return;
/* Periodically retry migrating the task to the preferred node */
interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
p->numa_migrate_retry = jiffies + interval;
/* Success if task is already running on preferred CPU */
if (task_node(p) == p->numa_preferred_nid)
return;
/* Otherwise, try migrate to a CPU on the preferred node */
task_numa_migrate(p);
}
/*
* Find out how many nodes the workload is actively running on. Do this by
* tracking the nodes from which NUMA hinting faults are triggered. This can
* be different from the set of nodes where the workload's memory is currently
* located.
*/
static void numa_group_count_active_nodes(struct numa_group *numa_group)
{
unsigned long faults, max_faults = 0;
int nid, active_nodes = 0;
for_each_node_state(nid, N_CPU) {
faults = group_faults_cpu(numa_group, nid);
if (faults > max_faults)
max_faults = faults;
}
for_each_node_state(nid, N_CPU) {
faults = group_faults_cpu(numa_group, nid);
if (faults * ACTIVE_NODE_FRACTION > max_faults)
active_nodes++;
}
numa_group->max_faults_cpu = max_faults;
numa_group->active_nodes = active_nodes;
}
/*
* When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
* increments. The more local the fault statistics are, the higher the scan
* period will be for the next scan window. If local/(local+remote) ratio is
* below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
* the scan period will decrease. Aim for 70% local accesses.
*/
#define NUMA_PERIOD_SLOTS 10
#define NUMA_PERIOD_THRESHOLD 7
/*
* Increase the scan period (slow down scanning) if the majority of
* our memory is already on our local node, or if the majority of
* the page accesses are shared with other processes.
* Otherwise, decrease the scan period.
*/
static void update_task_scan_period(struct task_struct *p,
unsigned long shared, unsigned long private)
{
unsigned int period_slot;
int lr_ratio, ps_ratio;
int diff;
unsigned long remote = p->numa_faults_locality[0];
unsigned long local = p->numa_faults_locality[1];
/*
* If there were no record hinting faults then either the task is
* completely idle or all activity is in areas that are not of interest
* to automatic numa balancing. Related to that, if there were failed
* migration then it implies we are migrating too quickly or the local
* node is overloaded. In either case, scan slower
*/
if (local + shared == 0 || p->numa_faults_locality[2]) {
p->numa_scan_period = min(p->numa_scan_period_max,
p->numa_scan_period << 1);
p->mm->numa_next_scan = jiffies +
msecs_to_jiffies(p->numa_scan_period);
return;
}
/*
* Prepare to scale scan period relative to the current period.
* == NUMA_PERIOD_THRESHOLD scan period stays the same
* < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
* >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
*/
period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
lr_ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
ps_ratio = (private * NUMA_PERIOD_SLOTS) / (private + shared);
if (ps_ratio >= NUMA_PERIOD_THRESHOLD) {
/*
* Most memory accesses are local. There is no need to
* do fast NUMA scanning, since memory is already local.
*/
int slot = ps_ratio - NUMA_PERIOD_THRESHOLD;
if (!slot)
slot = 1;
diff = slot * period_slot;
} else if (lr_ratio >= NUMA_PERIOD_THRESHOLD) {
/*
* Most memory accesses are shared with other tasks.
* There is no point in continuing fast NUMA scanning,
* since other tasks may just move the memory elsewhere.
*/
int slot = lr_ratio - NUMA_PERIOD_THRESHOLD;
if (!slot)
slot = 1;
diff = slot * period_slot;
} else {
/*
* Private memory faults exceed (SLOTS-THRESHOLD)/SLOTS,
* yet they are not on the local NUMA node. Speed up
* NUMA scanning to get the memory moved over.
*/
int ratio = max(lr_ratio, ps_ratio);
diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
}
p->numa_scan_period = clamp(p->numa_scan_period + diff,
task_scan_min(p), task_scan_max(p));
memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
}
/*
* Get the fraction of time the task has been running since the last
* NUMA placement cycle. The scheduler keeps similar statistics, but
* decays those on a 32ms period, which is orders of magnitude off
* from the dozens-of-seconds NUMA balancing period. Use the scheduler
* stats only if the task is so new there are no NUMA statistics yet.
*/
static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
{
u64 runtime, delta, now;
/* Use the start of this time slice to avoid calculations. */
now = p->se.exec_start;
runtime = p->se.sum_exec_runtime;
if (p->last_task_numa_placement) {
delta = runtime - p->last_sum_exec_runtime;
*period = now - p->last_task_numa_placement;
/* Avoid time going backwards, prevent potential divide error: */
if (unlikely((s64)*period < 0))
*period = 0;
} else {
delta = p->se.avg.load_sum;
*period = LOAD_AVG_MAX;
}
p->last_sum_exec_runtime = runtime;
p->last_task_numa_placement = now;
return delta;
}
/*
* Determine the preferred nid for a task in a numa_group. This needs to
* be done in a way that produces consistent results with group_weight,
* otherwise workloads might not converge.
*/
static int preferred_group_nid(struct task_struct *p, int nid)
{
nodemask_t nodes;
int dist;
/* Direct connections between all NUMA nodes. */
if (sched_numa_topology_type == NUMA_DIRECT)
return nid;
/*
* On a system with glueless mesh NUMA topology, group_weight
* scores nodes according to the number of NUMA hinting faults on
* both the node itself, and on nearby nodes.
*/
if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
unsigned long score, max_score = 0;
int node, max_node = nid;
dist = sched_max_numa_distance;
for_each_node_state(node, N_CPU) {
score = group_weight(p, node, dist);
if (score > max_score) {
max_score = score;
max_node = node;
}
}
return max_node;
}
/*
* Finding the preferred nid in a system with NUMA backplane
* interconnect topology is more involved. The goal is to locate
* tasks from numa_groups near each other in the system, and
* untangle workloads from different sides of the system. This requires
* searching down the hierarchy of node groups, recursively searching
* inside the highest scoring group of nodes. The nodemask tricks
* keep the complexity of the search down.
*/
nodes = node_states[N_CPU];
for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
unsigned long max_faults = 0;
nodemask_t max_group = NODE_MASK_NONE;
int a, b;
/* Are there nodes at this distance from each other? */
if (!find_numa_distance(dist))
continue;
for_each_node_mask(a, nodes) {
unsigned long faults = 0;
nodemask_t this_group;
nodes_clear(this_group);
/* Sum group's NUMA faults; includes a==b case. */
for_each_node_mask(b, nodes) {
if (node_distance(a, b) < dist) {
faults += group_faults(p, b);
node_set(b, this_group);
node_clear(b, nodes);
}
}
/* Remember the top group. */
if (faults > max_faults) {
max_faults = faults;
max_group = this_group;
/*
* subtle: at the smallest distance there is
* just one node left in each "group", the
* winner is the preferred nid.
*/
nid = a;
}
}
/* Next round, evaluate the nodes within max_group. */
if (!max_faults)
break;
nodes = max_group;
}
return nid;
}
static void task_numa_placement(struct task_struct *p)
{
int seq, nid, max_nid = NUMA_NO_NODE;
unsigned long max_faults = 0;
unsigned long fault_types[2] = { 0, 0 };
unsigned long total_faults;
u64 runtime, period;
spinlock_t *group_lock = NULL;
struct numa_group *ng;
/*
* The p->mm->numa_scan_seq field gets updated without
* exclusive access. Use READ_ONCE() here to ensure
* that the field is read in a single access:
*/
seq = READ_ONCE(p->mm->numa_scan_seq);
if (p->numa_scan_seq == seq)
return;
p->numa_scan_seq = seq;
p->numa_scan_period_max = task_scan_max(p);
total_faults = p->numa_faults_locality[0] +
p->numa_faults_locality[1];
runtime = numa_get_avg_runtime(p, &period);
/* If the task is part of a group prevent parallel updates to group stats */
ng = deref_curr_numa_group(p);
if (ng) {
group_lock = &ng->lock;
spin_lock_irq(group_lock);
}
/* Find the node with the highest number of faults */
for_each_online_node(nid) {
/* Keep track of the offsets in numa_faults array */
int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
unsigned long faults = 0, group_faults = 0;
int priv;
for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
long diff, f_diff, f_weight;
mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
/* Decay existing window, copy faults since last scan */
diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
fault_types[priv] += p->numa_faults[membuf_idx];
p->numa_faults[membuf_idx] = 0;
/*
* Normalize the faults_from, so all tasks in a group
* count according to CPU use, instead of by the raw
* number of faults. Tasks with little runtime have
* little over-all impact on throughput, and thus their
* faults are less important.
*/
f_weight = div64_u64(runtime << 16, period + 1);
f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
(total_faults + 1);
f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
p->numa_faults[cpubuf_idx] = 0;
p->numa_faults[mem_idx] += diff;
p->numa_faults[cpu_idx] += f_diff;
faults += p->numa_faults[mem_idx];
p->total_numa_faults += diff;
if (ng) {
/*
* safe because we can only change our own group
*
* mem_idx represents the offset for a given
* nid and priv in a specific region because it
* is at the beginning of the numa_faults array.
*/
ng->faults[mem_idx] += diff;
ng->faults[cpu_idx] += f_diff;
ng->total_faults += diff;
group_faults += ng->faults[mem_idx];
}
}
if (!ng) {
if (faults > max_faults) {
max_faults = faults;
max_nid = nid;
}
} else if (group_faults > max_faults) {
max_faults = group_faults;
max_nid = nid;
}
}
/* Cannot migrate task to CPU-less node */
if (max_nid != NUMA_NO_NODE && !node_state(max_nid, N_CPU)) {
int near_nid = max_nid;
int distance, near_distance = INT_MAX;
for_each_node_state(nid, N_CPU) {
distance = node_distance(max_nid, nid);
if (distance < near_distance) {
near_nid = nid;
near_distance = distance;
}
}
max_nid = near_nid;
}
if (ng) {
numa_group_count_active_nodes(ng);
spin_unlock_irq(group_lock);
max_nid = preferred_group_nid(p, max_nid);
}
if (max_faults) {
/* Set the new preferred node */
if (max_nid != p->numa_preferred_nid)
sched_setnuma(p, max_nid);
}
update_task_scan_period(p, fault_types[0], fault_types[1]);
}
static inline int get_numa_group(struct numa_group *grp)
{
return refcount_inc_not_zero(&grp->refcount);
}
static inline void put_numa_group(struct numa_group *grp)
{
if (refcount_dec_and_test(&grp->refcount))
kfree_rcu(grp, rcu);
}
static void task_numa_group(struct task_struct *p, int cpupid, int flags,
int *priv)
{
struct numa_group *grp, *my_grp;
struct task_struct *tsk;
bool join = false;
int cpu = cpupid_to_cpu(cpupid);
int i;
if (unlikely(!deref_curr_numa_group(p))) {
unsigned int size = sizeof(struct numa_group) +
NR_NUMA_HINT_FAULT_STATS *
nr_node_ids * sizeof(unsigned long);
grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
if (!grp)
return;
refcount_set(&grp->refcount, 1);
grp->active_nodes = 1;
grp->max_faults_cpu = 0;
spin_lock_init(&grp->lock);
grp->gid = p->pid;
for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
grp->faults[i] = p->numa_faults[i];
grp->total_faults = p->total_numa_faults;
grp->nr_tasks++;
rcu_assign_pointer(p->numa_group, grp);
}
rcu_read_lock();
tsk = READ_ONCE(cpu_rq(cpu)->curr);
if (!cpupid_match_pid(tsk, cpupid))
goto no_join;
grp = rcu_dereference(tsk->numa_group);
if (!grp)
goto no_join;
my_grp = deref_curr_numa_group(p);
if (grp == my_grp)
goto no_join;
/*
* Only join the other group if its bigger; if we're the bigger group,
* the other task will join us.
*/
if (my_grp->nr_tasks > grp->nr_tasks)
goto no_join;
/*
* Tie-break on the grp address.
*/
if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
goto no_join;
/* Always join threads in the same process. */
if (tsk->mm == current->mm)
join = true;
/* Simple filter to avoid false positives due to PID collisions */
if (flags & TNF_SHARED)
join = true;
/* Update priv based on whether false sharing was detected */
*priv = !join;
if (join && !get_numa_group(grp))
goto no_join;
rcu_read_unlock();
if (!join)
return;
WARN_ON_ONCE(irqs_disabled());
double_lock_irq(&my_grp->lock, &grp->lock);
for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
my_grp->faults[i] -= p->numa_faults[i];
grp->faults[i] += p->numa_faults[i];
}
my_grp->total_faults -= p->total_numa_faults;
grp->total_faults += p->total_numa_faults;
my_grp->nr_tasks--;
grp->nr_tasks++;
spin_unlock(&my_grp->lock);
spin_unlock_irq(&grp->lock);
rcu_assign_pointer(p->numa_group, grp);
put_numa_group(my_grp);
return;
no_join:
rcu_read_unlock();
return;
}
/*
* Get rid of NUMA statistics associated with a task (either current or dead).
* If @final is set, the task is dead and has reached refcount zero, so we can
* safely free all relevant data structures. Otherwise, there might be
* concurrent reads from places like load balancing and procfs, and we should
* reset the data back to default state without freeing ->numa_faults.
*/
void task_numa_free(struct task_struct *p, bool final)
{
/* safe: p either is current or is being freed by current */
struct numa_group *grp = rcu_dereference_raw(p->numa_group);
unsigned long *numa_faults = p->numa_faults;
unsigned long flags;
int i;
if (!numa_faults)
return;
if (grp) {
spin_lock_irqsave(&grp->lock, flags);
for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
grp->faults[i] -= p->numa_faults[i];
grp->total_faults -= p->total_numa_faults;
grp->nr_tasks--;
spin_unlock_irqrestore(&grp->lock, flags);
RCU_INIT_POINTER(p->numa_group, NULL);
put_numa_group(grp);
}
if (final) {
p->numa_faults = NULL;
kfree(numa_faults);
} else {
p->total_numa_faults = 0;
for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
numa_faults[i] = 0;
}
}
/*
* Got a PROT_NONE fault for a page on @node.
*/
void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
{
struct task_struct *p = current;
bool migrated = flags & TNF_MIGRATED;
int cpu_node = task_node(current);
int local = !!(flags & TNF_FAULT_LOCAL);
struct numa_group *ng;
int priv;
if (!static_branch_likely(&sched_numa_balancing))
return;
/* for example, ksmd faulting in a user's mm */
if (!p->mm)
return;
/*
* NUMA faults statistics are unnecessary for the slow memory
* node for memory tiering mode.
*/
if (!node_is_toptier(mem_node) &&
(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING ||
!cpupid_valid(last_cpupid)))
return;
/* Allocate buffer to track faults on a per-node basis */
if (unlikely(!p->numa_faults)) {
int size = sizeof(*p->numa_faults) *
NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
if (!p->numa_faults)
return;
p->total_numa_faults = 0;
memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
}
/*
* First accesses are treated as private, otherwise consider accesses
* to be private if the accessing pid has not changed
*/
if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
priv = 1;
} else {
priv = cpupid_match_pid(p, last_cpupid);
if (!priv && !(flags & TNF_NO_GROUP))
task_numa_group(p, last_cpupid, flags, &priv);
}
/*
* If a workload spans multiple NUMA nodes, a shared fault that
* occurs wholly within the set of nodes that the workload is
* actively using should be counted as local. This allows the
* scan rate to slow down when a workload has settled down.
*/
ng = deref_curr_numa_group(p);
if (!priv && !local && ng && ng->active_nodes > 1 &&
numa_is_active_node(cpu_node, ng) &&
numa_is_active_node(mem_node, ng))
local = 1;
/*
* Retry to migrate task to preferred node periodically, in case it
* previously failed, or the scheduler moved us.
*/
if (time_after(jiffies, p->numa_migrate_retry)) {
task_numa_placement(p);
numa_migrate_preferred(p);
}
if (migrated)
p->numa_pages_migrated += pages;
if (flags & TNF_MIGRATE_FAIL)
p->numa_faults_locality[2] += pages;
p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
p->numa_faults_locality[local] += pages;
}
static void reset_ptenuma_scan(struct task_struct *p)
{
/*
* We only did a read acquisition of the mmap sem, so
* p->mm->numa_scan_seq is written to without exclusive access
* and the update is not guaranteed to be atomic. That's not
* much of an issue though, since this is just used for
* statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
* expensive, to avoid any form of compiler optimizations:
*/
WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
p->mm->numa_scan_offset = 0;
}
static bool vma_is_accessed(struct vm_area_struct *vma)
{
unsigned long pids;
/*
* Allow unconditional access first two times, so that all the (pages)
* of VMAs get prot_none fault introduced irrespective of accesses.
* This is also done to avoid any side effect of task scanning
* amplifying the unfairness of disjoint set of VMAs' access.
*/
if (READ_ONCE(current->mm->numa_scan_seq) < 2)
return true;
pids = vma->numab_state->access_pids[0] | vma->numab_state->access_pids[1];
return test_bit(hash_32(current->pid, ilog2(BITS_PER_LONG)), &pids);
}
#define VMA_PID_RESET_PERIOD (4 * sysctl_numa_balancing_scan_delay)
/*
* The expensive part of numa migration is done from task_work context.
* Triggered from task_tick_numa().
*/
static void task_numa_work(struct callback_head *work)
{
unsigned long migrate, next_scan, now = jiffies;
struct task_struct *p = current;
struct mm_struct *mm = p->mm;
u64 runtime = p->se.sum_exec_runtime;
struct vm_area_struct *vma;
unsigned long start, end;
unsigned long nr_pte_updates = 0;
long pages, virtpages;
struct vma_iterator vmi;
SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work));
work->next = work;
/*
* Who cares about NUMA placement when they're dying.
*
* NOTE: make sure not to dereference p->mm before this check,
* exit_task_work() happens _after_ exit_mm() so we could be called
* without p->mm even though we still had it when we enqueued this
* work.
*/
if (p->flags & PF_EXITING)
return;
if (!mm->numa_next_scan) {
mm->numa_next_scan = now +
msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
}
/*
* Enforce maximal scan/migration frequency..
*/
migrate = mm->numa_next_scan;
if (time_before(now, migrate))
return;
if (p->numa_scan_period == 0) {
p->numa_scan_period_max = task_scan_max(p);
p->numa_scan_period = task_scan_start(p);
}
next_scan = now + msecs_to_jiffies(p->numa_scan_period);
if (!try_cmpxchg(&mm->numa_next_scan, &migrate, next_scan))
return;
/*
* Delay this task enough that another task of this mm will likely win
* the next time around.
*/
p->node_stamp += 2 * TICK_NSEC;
start = mm->numa_scan_offset;
pages = sysctl_numa_balancing_scan_size;
pages <<= 20 - PAGE_SHIFT; /* MB in pages */
virtpages = pages * 8; /* Scan up to this much virtual space */
if (!pages)
return;
if (!mmap_read_trylock(mm))
return;
vma_iter_init(&vmi, mm, start);
vma = vma_next(&vmi);
if (!vma) {
reset_ptenuma_scan(p);
start = 0;
vma_iter_set(&vmi, start);
vma = vma_next(&vmi);
}
do {
if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
continue;
}
/*
* Shared library pages mapped by multiple processes are not
* migrated as it is expected they are cache replicated. Avoid
* hinting faults in read-only file-backed mappings or the vdso
* as migrating the pages will be of marginal benefit.
*/
if (!vma->vm_mm ||
(vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
continue;
/*
* Skip inaccessible VMAs to avoid any confusion between
* PROT_NONE and NUMA hinting ptes
*/
if (!vma_is_accessible(vma))
continue;
/* Initialise new per-VMA NUMAB state. */
if (!vma->numab_state) {
vma->numab_state = kzalloc(sizeof(struct vma_numab_state),
GFP_KERNEL);
if (!vma->numab_state)
continue;
vma->numab_state->next_scan = now +
msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
/* Reset happens after 4 times scan delay of scan start */
vma->numab_state->next_pid_reset = vma->numab_state->next_scan +
msecs_to_jiffies(VMA_PID_RESET_PERIOD);
}
/*
* Scanning the VMA's of short lived tasks add more overhead. So
* delay the scan for new VMAs.
*/
if (mm->numa_scan_seq && time_before(jiffies,
vma->numab_state->next_scan))
continue;
/* Do not scan the VMA if task has not accessed */
if (!vma_is_accessed(vma))
continue;
/*
* RESET access PIDs regularly for old VMAs. Resetting after checking
* vma for recent access to avoid clearing PID info before access..
*/
if (mm->numa_scan_seq &&
time_after(jiffies, vma->numab_state->next_pid_reset)) {
vma->numab_state->next_pid_reset = vma->numab_state->next_pid_reset +
msecs_to_jiffies(VMA_PID_RESET_PERIOD);
vma->numab_state->access_pids[0] = READ_ONCE(vma->numab_state->access_pids[1]);
vma->numab_state->access_pids[1] = 0;
}
do {
start = max(start, vma->vm_start);
end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
end = min(end, vma->vm_end);
nr_pte_updates = change_prot_numa(vma, start, end);
/*
* Try to scan sysctl_numa_balancing_size worth of
* hpages that have at least one present PTE that
* is not already pte-numa. If the VMA contains
* areas that are unused or already full of prot_numa
* PTEs, scan up to virtpages, to skip through those
* areas faster.
*/
if (nr_pte_updates)
pages -= (end - start) >> PAGE_SHIFT;
virtpages -= (end - start) >> PAGE_SHIFT;
start = end;
if (pages <= 0 || virtpages <= 0)
goto out;
cond_resched();
} while (end != vma->vm_end);
} for_each_vma(vmi, vma);
out:
/*
* It is possible to reach the end of the VMA list but the last few
* VMAs are not guaranteed to the vma_migratable. If they are not, we
* would find the !migratable VMA on the next scan but not reset the
* scanner to the start so check it now.
*/
if (vma)
mm->numa_scan_offset = start;
else
reset_ptenuma_scan(p);
mmap_read_unlock(mm);
/*
* Make sure tasks use at least 32x as much time to run other code
* than they used here, to limit NUMA PTE scanning overhead to 3% max.
* Usually update_task_scan_period slows down scanning enough; on an
* overloaded system we need to limit overhead on a per task basis.
*/
if (unlikely(p->se.sum_exec_runtime != runtime)) {
u64 diff = p->se.sum_exec_runtime - runtime;
p->node_stamp += 32 * diff;
}
}
void init_numa_balancing(unsigned long clone_flags, struct task_struct *p)
{
int mm_users = 0;
struct mm_struct *mm = p->mm;
if (mm) {
mm_users = atomic_read(&mm->mm_users);
if (mm_users == 1) {
mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
mm->numa_scan_seq = 0;
}
}
p->node_stamp = 0;
p->numa_scan_seq = mm ? mm->numa_scan_seq : 0;
p->numa_scan_period = sysctl_numa_balancing_scan_delay;
p->numa_migrate_retry = 0;
/* Protect against double add, see task_tick_numa and task_numa_work */
p->numa_work.next = &p->numa_work;
p->numa_faults = NULL;
p->numa_pages_migrated = 0;
p->total_numa_faults = 0;
RCU_INIT_POINTER(p->numa_group, NULL);
p->last_task_numa_placement = 0;
p->last_sum_exec_runtime = 0;
init_task_work(&p->numa_work, task_numa_work);
/* New address space, reset the preferred nid */
if (!(clone_flags & CLONE_VM)) {
p->numa_preferred_nid = NUMA_NO_NODE;
return;
}
/*
* New thread, keep existing numa_preferred_nid which should be copied
* already by arch_dup_task_struct but stagger when scans start.
*/
if (mm) {
unsigned int delay;
delay = min_t(unsigned int, task_scan_max(current),
current->numa_scan_period * mm_users * NSEC_PER_MSEC);
delay += 2 * TICK_NSEC;
p->node_stamp = delay;
}
}
/*
* Drive the periodic memory faults..
*/
static void task_tick_numa(struct rq *rq, struct task_struct *curr)
{
struct callback_head *work = &curr->numa_work;
u64 period, now;
/*
* We don't care about NUMA placement if we don't have memory.
*/
if (!curr->mm || (curr->flags & (PF_EXITING | PF_KTHREAD)) || work->next != work)
return;
/*
* Using runtime rather than walltime has the dual advantage that
* we (mostly) drive the selection from busy threads and that the
* task needs to have done some actual work before we bother with
* NUMA placement.
*/
now = curr->se.sum_exec_runtime;
period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
if (now > curr->node_stamp + period) {
if (!curr->node_stamp)
curr->numa_scan_period = task_scan_start(curr);
curr->node_stamp += period;
if (!time_before(jiffies, curr->mm->numa_next_scan))
task_work_add(curr, work, TWA_RESUME);
}
}
static void update_scan_period(struct task_struct *p, int new_cpu)
{
int src_nid = cpu_to_node(task_cpu(p));
int dst_nid = cpu_to_node(new_cpu);
if (!static_branch_likely(&sched_numa_balancing))
return;
if (!p->mm || !p->numa_faults || (p->flags & PF_EXITING))
return;
if (src_nid == dst_nid)
return;
/*
* Allow resets if faults have been trapped before one scan
* has completed. This is most likely due to a new task that
* is pulled cross-node due to wakeups or load balancing.
*/
if (p->numa_scan_seq) {
/*
* Avoid scan adjustments if moving to the preferred
* node or if the task was not previously running on
* the preferred node.
*/
if (dst_nid == p->numa_preferred_nid ||
(p->numa_preferred_nid != NUMA_NO_NODE &&
src_nid != p->numa_preferred_nid))
return;
}
p->numa_scan_period = task_scan_start(p);
}
#else
static void task_tick_numa(struct rq *rq, struct task_struct *curr)
{
}
static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
{
}
static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
{
}
static inline void update_scan_period(struct task_struct *p, int new_cpu)
{
}
#endif /* CONFIG_NUMA_BALANCING */
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
update_load_add(&cfs_rq->load, se->load.weight);
#ifdef CONFIG_SMP
if (entity_is_task(se)) {
struct rq *rq = rq_of(cfs_rq);
account_numa_enqueue(rq, task_of(se));
list_add(&se->group_node, &rq->cfs_tasks);
}
#endif
cfs_rq->nr_running++;
if (se_is_idle(se))
cfs_rq->idle_nr_running++;
}
static void
account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
update_load_sub(&cfs_rq->load, se->load.weight);
#ifdef CONFIG_SMP
if (entity_is_task(se)) {
account_numa_dequeue(rq_of(cfs_rq), task_of(se));
list_del_init(&se->group_node);
}
#endif
cfs_rq->nr_running--;
if (se_is_idle(se))
cfs_rq->idle_nr_running--;
}
/*
* Signed add and clamp on underflow.
*
* Explicitly do a load-store to ensure the intermediate value never hits
* memory. This allows lockless observations without ever seeing the negative
* values.
*/
#define add_positive(_ptr, _val) do { \
typeof(_ptr) ptr = (_ptr); \
typeof(_val) val = (_val); \
typeof(*ptr) res, var = READ_ONCE(*ptr); \
\
res = var + val; \
\
if (val < 0 && res > var) \
res = 0; \
\
WRITE_ONCE(*ptr, res); \
} while (0)
/*
* Unsigned subtract and clamp on underflow.
*
* Explicitly do a load-store to ensure the intermediate value never hits
* memory. This allows lockless observations without ever seeing the negative
* values.
*/
#define sub_positive(_ptr, _val) do { \
typeof(_ptr) ptr = (_ptr); \
typeof(*ptr) val = (_val); \
typeof(*ptr) res, var = READ_ONCE(*ptr); \
res = var - val; \
if (res > var) \
res = 0; \
WRITE_ONCE(*ptr, res); \
} while (0)
/*
* Remove and clamp on negative, from a local variable.
*
* A variant of sub_positive(), which does not use explicit load-store
* and is thus optimized for local variable updates.
*/
#define lsub_positive(_ptr, _val) do { \
typeof(_ptr) ptr = (_ptr); \
*ptr -= min_t(typeof(*ptr), *ptr, _val); \
} while (0)
#ifdef CONFIG_SMP
static inline void
enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
cfs_rq->avg.load_avg += se->avg.load_avg;
cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum;
}
static inline void
dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
sub_positive(&cfs_rq->avg.load_sum, se_weight(se) * se->avg.load_sum);
/* See update_cfs_rq_load_avg() */
cfs_rq->avg.load_sum = max_t(u32, cfs_rq->avg.load_sum,
cfs_rq->avg.load_avg * PELT_MIN_DIVIDER);
}
#else
static inline void
enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
static inline void
dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
#endif
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
unsigned long weight)
{
if (se->on_rq) {
/* commit outstanding execution time */
if (cfs_rq->curr == se)
update_curr(cfs_rq);
update_load_sub(&cfs_rq->load, se->load.weight);
}
dequeue_load_avg(cfs_rq, se);
update_load_set(&se->load, weight);
#ifdef CONFIG_SMP
do {
u32 divider = get_pelt_divider(&se->avg);
se->avg.load_avg = div_u64(se_weight(se) * se->avg.load_sum, divider);
} while (0);
#endif
enqueue_load_avg(cfs_rq, se);
if (se->on_rq)
update_load_add(&cfs_rq->load, se->load.weight);
}
void reweight_task(struct task_struct *p, int prio)
{
struct sched_entity *se = &p->se;
struct cfs_rq *cfs_rq = cfs_rq_of(se);
struct load_weight *load = &se->load;
unsigned long weight = scale_load(sched_prio_to_weight[prio]);
reweight_entity(cfs_rq, se, weight);
load->inv_weight = sched_prio_to_wmult[prio];
}
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
#ifdef CONFIG_FAIR_GROUP_SCHED
#ifdef CONFIG_SMP
/*
* All this does is approximate the hierarchical proportion which includes that
* global sum we all love to hate.
*
* That is, the weight of a group entity, is the proportional share of the
* group weight based on the group runqueue weights. That is:
*
* tg->weight * grq->load.weight
* ge->load.weight = ----------------------------- (1)
* \Sum grq->load.weight
*
* Now, because computing that sum is prohibitively expensive to compute (been
* there, done that) we approximate it with this average stuff. The average
* moves slower and therefore the approximation is cheaper and more stable.
*
* So instead of the above, we substitute:
*
* grq->load.weight -> grq->avg.load_avg (2)
*
* which yields the following:
*
* tg->weight * grq->avg.load_avg
* ge->load.weight = ------------------------------ (3)
* tg->load_avg
*
* Where: tg->load_avg ~= \Sum grq->avg.load_avg
*
* That is shares_avg, and it is right (given the approximation (2)).
*
* The problem with it is that because the average is slow -- it was designed
* to be exactly that of course -- this leads to transients in boundary
* conditions. In specific, the case where the group was idle and we start the
* one task. It takes time for our CPU's grq->avg.load_avg to build up,
* yielding bad latency etc..
*
* Now, in that special case (1) reduces to:
*
* tg->weight * grq->load.weight
* ge->load.weight = ----------------------------- = tg->weight (4)
* grp->load.weight
*
* That is, the sum collapses because all other CPUs are idle; the UP scenario.
*
* So what we do is modify our approximation (3) to approach (4) in the (near)
* UP case, like:
*
* ge->load.weight =
*
* tg->weight * grq->load.weight
* --------------------------------------------------- (5)
* tg->load_avg - grq->avg.load_avg + grq->load.weight
*
* But because grq->load.weight can drop to 0, resulting in a divide by zero,
* we need to use grq->avg.load_avg as its lower bound, which then gives:
*
*
* tg->weight * grq->load.weight
* ge->load.weight = ----------------------------- (6)
* tg_load_avg'
*
* Where:
*
* tg_load_avg' = tg->load_avg - grq->avg.load_avg +
* max(grq->load.weight, grq->avg.load_avg)
*
* And that is shares_weight and is icky. In the (near) UP case it approaches
* (4) while in the normal case it approaches (3). It consistently
* overestimates the ge->load.weight and therefore:
*
* \Sum ge->load.weight >= tg->weight
*
* hence icky!
*/
static long calc_group_shares(struct cfs_rq *cfs_rq)
{
long tg_weight, tg_shares, load, shares;
struct task_group *tg = cfs_rq->tg;
tg_shares = READ_ONCE(tg->shares);
load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg);
tg_weight = atomic_long_read(&tg->load_avg);
/* Ensure tg_weight >= load */
tg_weight -= cfs_rq->tg_load_avg_contrib;
tg_weight += load;
shares = (tg_shares * load);
if (tg_weight)
shares /= tg_weight;
/*
* MIN_SHARES has to be unscaled here to support per-CPU partitioning
* of a group with small tg->shares value. It is a floor value which is
* assigned as a minimum load.weight to the sched_entity representing
* the group on a CPU.
*
* E.g. on 64-bit for a group with tg->shares of scale_load(15)=15*1024
* on an 8-core system with 8 tasks each runnable on one CPU shares has
* to be 15*1024*1/8=1920 instead of scale_load(MIN_SHARES)=2*1024. In
* case no task is runnable on a CPU MIN_SHARES=2 should be returned
* instead of 0.
*/
return clamp_t(long, shares, MIN_SHARES, tg_shares);
}
#endif /* CONFIG_SMP */
/*
* Recomputes the group entity based on the current state of its group
* runqueue.
*/
static void update_cfs_group(struct sched_entity *se)
{
struct cfs_rq *gcfs_rq = group_cfs_rq(se);
long shares;
if (!gcfs_rq)
return;
if (throttled_hierarchy(gcfs_rq))
return;
#ifndef CONFIG_SMP
shares = READ_ONCE(gcfs_rq->tg->shares);
if (likely(se->load.weight == shares))
return;
#else
shares = calc_group_shares(gcfs_rq);
#endif
reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
static inline void update_cfs_group(struct sched_entity *se)
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */
static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags)
{
struct rq *rq = rq_of(cfs_rq);
if (&rq->cfs == cfs_rq) {
/*
* There are a few boundary cases this might miss but it should
* get called often enough that that should (hopefully) not be
* a real problem.
*
* It will not get called when we go idle, because the idle
* thread is a different class (!fair), nor will the utilization
* number include things like RT tasks.
*
* As is, the util number is not freq-invariant (we'd have to
* implement arch_scale_freq_capacity() for that).
*
* See cpu_util_cfs().
*/
cpufreq_update_util(rq, flags);
}
}
#ifdef CONFIG_SMP
static inline bool load_avg_is_decayed(struct sched_avg *sa)
{
if (sa->load_sum)
return false;
if (sa->util_sum)
return false;
if (sa->runnable_sum)
return false;
/*
* _avg must be null when _sum are null because _avg = _sum / divider
* Make sure that rounding and/or propagation of PELT values never
* break this.
*/
SCHED_WARN_ON(sa->load_avg ||
sa->util_avg ||
sa->runnable_avg);
return true;
}
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
return u64_u32_load_copy(cfs_rq->avg.last_update_time,
cfs_rq->last_update_time_copy);
}
#ifdef CONFIG_FAIR_GROUP_SCHED
/*
* Because list_add_leaf_cfs_rq always places a child cfs_rq on the list
* immediately before a parent cfs_rq, and cfs_rqs are removed from the list
* bottom-up, we only have to test whether the cfs_rq before us on the list
* is our child.
* If cfs_rq is not on the list, test whether a child needs its to be added to
* connect a branch to the tree * (see list_add_leaf_cfs_rq() for details).
*/
static inline bool child_cfs_rq_on_list(struct cfs_rq *cfs_rq)
{
struct cfs_rq *prev_cfs_rq;
struct list_head *prev;
if (cfs_rq->on_list) {
prev = cfs_rq->leaf_cfs_rq_list.prev;
} else {
struct rq *rq = rq_of(cfs_rq);
prev = rq->tmp_alone_branch;
}
prev_cfs_rq = container_of(prev, struct cfs_rq, leaf_cfs_rq_list);
return (prev_cfs_rq->tg->parent == cfs_rq->tg);
}
static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
{
if (cfs_rq->load.weight)
return false;
if (!load_avg_is_decayed(&cfs_rq->avg))
return false;
if (child_cfs_rq_on_list(cfs_rq))
return false;
return true;
}
/**
* update_tg_load_avg - update the tg's load avg
* @cfs_rq: the cfs_rq whose avg changed
*
* This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load.
* However, because tg->load_avg is a global value there are performance
* considerations.
*
* In order to avoid having to look at the other cfs_rq's, we use a
* differential update where we store the last value we propagated. This in
* turn allows skipping updates if the differential is 'small'.
*
* Updating tg's load_avg is necessary before update_cfs_share().
*/
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq)
{
long delta;
u64 now;
/*
* No need to update load_avg for root_task_group as it is not used.
*/
if (cfs_rq->tg == &root_task_group)
return;
/*
* For migration heavy workloads, access to tg->load_avg can be
* unbound. Limit the update rate to at most once per ms.
*/
now = sched_clock_cpu(cpu_of(rq_of(cfs_rq)));
if (now - cfs_rq->last_update_tg_load_avg < NSEC_PER_MSEC)
return;
delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
if (abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
atomic_long_add(delta, &cfs_rq->tg->load_avg);
cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
cfs_rq->last_update_tg_load_avg = now;
}
}
/*
* Called within set_task_rq() right before setting a task's CPU. The
* caller only guarantees p->pi_lock is held; no other assumptions,
* including the state of rq->lock, should be made.
*/
void set_task_rq_fair(struct sched_entity *se,
struct cfs_rq *prev, struct cfs_rq *next)
{
u64 p_last_update_time;
u64 n_last_update_time;
if (!sched_feat(ATTACH_AGE_LOAD))
return;
/*
* We are supposed to update the task to "current" time, then its up to
* date and ready to go to new CPU/cfs_rq. But we have difficulty in
* getting what current time is, so simply throw away the out-of-date
* time. This will result in the wakee task is less decayed, but giving
* the wakee more load sounds not bad.
*/
if (!(se->avg.last_update_time && prev))
return;
p_last_update_time = cfs_rq_last_update_time(prev);
n_last_update_time = cfs_rq_last_update_time(next);
__update_load_avg_blocked_se(p_last_update_time, se);
se->avg.last_update_time = n_last_update_time;
}
/*
* When on migration a sched_entity joins/leaves the PELT hierarchy, we need to
* propagate its contribution. The key to this propagation is the invariant
* that for each group:
*
* ge->avg == grq->avg (1)
*
* _IFF_ we look at the pure running and runnable sums. Because they
* represent the very same entity, just at different points in the hierarchy.
*
* Per the above update_tg_cfs_util() and update_tg_cfs_runnable() are trivial
* and simply copies the running/runnable sum over (but still wrong, because
* the group entity and group rq do not have their PELT windows aligned).
*
* However, update_tg_cfs_load() is more complex. So we have:
*
* ge->avg.load_avg = ge->load.weight * ge->avg.runnable_avg (2)
*
* And since, like util, the runnable part should be directly transferable,
* the following would _appear_ to be the straight forward approach:
*
* grq->avg.load_avg = grq->load.weight * grq->avg.runnable_avg (3)
*
* And per (1) we have:
*
* ge->avg.runnable_avg == grq->avg.runnable_avg
*
* Which gives:
*
* ge->load.weight * grq->avg.load_avg
* ge->avg.load_avg = ----------------------------------- (4)
* grq->load.weight
*
* Except that is wrong!
*
* Because while for entities historical weight is not important and we
* really only care about our future and therefore can consider a pure
* runnable sum, runqueues can NOT do this.
*
* We specifically want runqueues to have a load_avg that includes
* historical weights. Those represent the blocked load, the load we expect
* to (shortly) return to us. This only works by keeping the weights as
* integral part of the sum. We therefore cannot decompose as per (3).
*
* Another reason this doesn't work is that runnable isn't a 0-sum entity.
* Imagine a rq with 2 tasks that each are runnable 2/3 of the time. Then the
* rq itself is runnable anywhere between 2/3 and 1 depending on how the
* runnable section of these tasks overlap (or not). If they were to perfectly
* align the rq as a whole would be runnable 2/3 of the time. If however we
* always have at least 1 runnable task, the rq as a whole is always runnable.
*
* So we'll have to approximate.. :/
*
* Given the constraint:
*
* ge->avg.running_sum <= ge->avg.runnable_sum <= LOAD_AVG_MAX
*
* We can construct a rule that adds runnable to a rq by assuming minimal
* overlap.
*
* On removal, we'll assume each task is equally runnable; which yields:
*
* grq->avg.runnable_sum = grq->avg.load_sum / grq->load.weight
*
* XXX: only do this for the part of runnable > running ?
*
*/
static inline void
update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
{
long delta_sum, delta_avg = gcfs_rq->avg.util_avg - se->avg.util_avg;
u32 new_sum, divider;
/* Nothing to update */
if (!delta_avg)
return;
/*
* cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
* See ___update_load_avg() for details.
*/
divider = get_pelt_divider(&cfs_rq->avg);
/* Set new sched_entity's utilization */
se->avg.util_avg = gcfs_rq->avg.util_avg;
new_sum = se->avg.util_avg * divider;
delta_sum = (long)new_sum - (long)se->avg.util_sum;
se->avg.util_sum = new_sum;
/* Update parent cfs_rq utilization */
add_positive(&cfs_rq->avg.util_avg, delta_avg);
add_positive(&cfs_rq->avg.util_sum, delta_sum);
/* See update_cfs_rq_load_avg() */
cfs_rq->avg.util_sum = max_t(u32, cfs_rq->avg.util_sum,
cfs_rq->avg.util_avg * PELT_MIN_DIVIDER);
}
static inline void
update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
{
long delta_sum, delta_avg = gcfs_rq->avg.runnable_avg - se->avg.runnable_avg;
u32 new_sum, divider;
/* Nothing to update */
if (!delta_avg)
return;
/*
* cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
* See ___update_load_avg() for details.
*/
divider = get_pelt_divider(&cfs_rq->avg);
/* Set new sched_entity's runnable */
se->avg.runnable_avg = gcfs_rq->avg.runnable_avg;
new_sum = se->avg.runnable_avg * divider;
delta_sum = (long)new_sum - (long)se->avg.runnable_sum;
se->avg.runnable_sum = new_sum;
/* Update parent cfs_rq runnable */
add_positive(&cfs_rq->avg.runnable_avg, delta_avg);
add_positive(&cfs_rq->avg.runnable_sum, delta_sum);
/* See update_cfs_rq_load_avg() */
cfs_rq->avg.runnable_sum = max_t(u32, cfs_rq->avg.runnable_sum,
cfs_rq->avg.runnable_avg * PELT_MIN_DIVIDER);
}
static inline void
update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
{
long delta_avg, running_sum, runnable_sum = gcfs_rq->prop_runnable_sum;
unsigned long load_avg;
u64 load_sum = 0;
s64 delta_sum;
u32 divider;
if (!runnable_sum)
return;
gcfs_rq->prop_runnable_sum = 0;
/*
* cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
* See ___update_load_avg() for details.
*/
divider = get_pelt_divider(&cfs_rq->avg);
if (runnable_sum >= 0) {
/*
* Add runnable; clip at LOAD_AVG_MAX. Reflects that until
* the CPU is saturated running == runnable.
*/
runnable_sum += se->avg.load_sum;
runnable_sum = min_t(long, runnable_sum, divider);
} else {
/*
* Estimate the new unweighted runnable_sum of the gcfs_rq by
* assuming all tasks are equally runnable.
*/
if (scale_load_down(gcfs_rq->load.weight)) {
load_sum = div_u64(gcfs_rq->avg.load_sum,
scale_load_down(gcfs_rq->load.weight));
}
/* But make sure to not inflate se's runnable */
runnable_sum = min(se->avg.load_sum, load_sum);
}
/*
* runnable_sum can't be lower than running_sum
* Rescale running sum to be in the same range as runnable sum
* running_sum is in [0 : LOAD_AVG_MAX << SCHED_CAPACITY_SHIFT]
* runnable_sum is in [0 : LOAD_AVG_MAX]
*/
running_sum = se->avg.util_sum >> SCHED_CAPACITY_SHIFT;
runnable_sum = max(runnable_sum, running_sum);
load_sum = se_weight(se) * runnable_sum;
load_avg = div_u64(load_sum, divider);
delta_avg = load_avg - se->avg.load_avg;
if (!delta_avg)
return;
delta_sum = load_sum - (s64)se_weight(se) * se->avg.load_sum;
se->avg.load_sum = runnable_sum;
se->avg.load_avg = load_avg;
add_positive(&cfs_rq->avg.load_avg, delta_avg);
add_positive(&cfs_rq->avg.load_sum, delta_sum);
/* See update_cfs_rq_load_avg() */
cfs_rq->avg.load_sum = max_t(u32, cfs_rq->avg.load_sum,
cfs_rq->avg.load_avg * PELT_MIN_DIVIDER);
}
static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum)
{
cfs_rq->propagate = 1;
cfs_rq->prop_runnable_sum += runnable_sum;
}
/* Update task and its cfs_rq load average */
static inline int propagate_entity_load_avg(struct sched_entity *se)
{
struct cfs_rq *cfs_rq, *gcfs_rq;
if (entity_is_task(se))
return 0;
gcfs_rq = group_cfs_rq(se);
if (!gcfs_rq->propagate)
return 0;
gcfs_rq->propagate = 0;
cfs_rq = cfs_rq_of(se);
add_tg_cfs_propagate(cfs_rq, gcfs_rq->prop_runnable_sum);
update_tg_cfs_util(cfs_rq, se, gcfs_rq);
update_tg_cfs_runnable(cfs_rq, se, gcfs_rq);
update_tg_cfs_load(cfs_rq, se, gcfs_rq);
trace_pelt_cfs_tp(cfs_rq);
trace_pelt_se_tp(se);
return 1;
}
/*
* Check if we need to update the load and the utilization of a blocked
* group_entity:
*/
static inline bool skip_blocked_update(struct sched_entity *se)
{
struct cfs_rq *gcfs_rq = group_cfs_rq(se);
/*
* If sched_entity still have not zero load or utilization, we have to
* decay it:
*/
if (se->avg.load_avg || se->avg.util_avg)
return false;
/*
* If there is a pending propagation, we have to update the load and
* the utilization of the sched_entity:
*/
if (gcfs_rq->propagate)
return false;
/*
* Otherwise, the load and the utilization of the sched_entity is
* already zero and there is no pending propagation, so it will be a
* waste of time to try to decay it:
*/
return true;
}
#else /* CONFIG_FAIR_GROUP_SCHED */
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq) {}
static inline int propagate_entity_load_avg(struct sched_entity *se)
{
return 0;
}
static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum) {}
#endif /* CONFIG_FAIR_GROUP_SCHED */
#ifdef CONFIG_NO_HZ_COMMON
static inline void migrate_se_pelt_lag(struct sched_entity *se)
{
u64 throttled = 0, now, lut;
struct cfs_rq *cfs_rq;
struct rq *rq;
bool is_idle;
if (load_avg_is_decayed(&se->avg))
return;
cfs_rq = cfs_rq_of(se);
rq = rq_of(cfs_rq);
rcu_read_lock();
is_idle = is_idle_task(rcu_dereference(rq->curr));
rcu_read_unlock();
/*
* The lag estimation comes with a cost we don't want to pay all the
* time. Hence, limiting to the case where the source CPU is idle and
* we know we are at the greatest risk to have an outdated clock.
*/
if (!is_idle)
return;
/*
* Estimated "now" is: last_update_time + cfs_idle_lag + rq_idle_lag, where:
*
* last_update_time (the cfs_rq's last_update_time)
* = cfs_rq_clock_pelt()@cfs_rq_idle
* = rq_clock_pelt()@cfs_rq_idle
* - cfs->throttled_clock_pelt_time@cfs_rq_idle
*
* cfs_idle_lag (delta between rq's update and cfs_rq's update)
* = rq_clock_pelt()@rq_idle - rq_clock_pelt()@cfs_rq_idle
*
* rq_idle_lag (delta between now and rq's update)
* = sched_clock_cpu() - rq_clock()@rq_idle
*
* We can then write:
*
* now = rq_clock_pelt()@rq_idle - cfs->throttled_clock_pelt_time +
* sched_clock_cpu() - rq_clock()@rq_idle
* Where:
* rq_clock_pelt()@rq_idle is rq->clock_pelt_idle
* rq_clock()@rq_idle is rq->clock_idle
* cfs->throttled_clock_pelt_time@cfs_rq_idle
* is cfs_rq->throttled_pelt_idle
*/
#ifdef CONFIG_CFS_BANDWIDTH
throttled = u64_u32_load(cfs_rq->throttled_pelt_idle);
/* The clock has been stopped for throttling */
if (throttled == U64_MAX)
return;
#endif
now = u64_u32_load(rq->clock_pelt_idle);
/*
* Paired with _update_idle_rq_clock_pelt(). It ensures at the worst case
* is observed the old clock_pelt_idle value and the new clock_idle,
* which lead to an underestimation. The opposite would lead to an
* overestimation.
*/
smp_rmb();
lut = cfs_rq_last_update_time(cfs_rq);
now -= throttled;
if (now < lut)
/*
* cfs_rq->avg.last_update_time is more recent than our
* estimation, let's use it.
*/
now = lut;
else
now += sched_clock_cpu(cpu_of(rq)) - u64_u32_load(rq->clock_idle);
__update_load_avg_blocked_se(now, se);
}
#else
static void migrate_se_pelt_lag(struct sched_entity *se) {}
#endif
/**
* update_cfs_rq_load_avg - update the cfs_rq's load/util averages
* @now: current time, as per cfs_rq_clock_pelt()
* @cfs_rq: cfs_rq to update
*
* The cfs_rq avg is the direct sum of all its entities (blocked and runnable)
* avg. The immediate corollary is that all (fair) tasks must be attached.
*
* cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
*
* Return: true if the load decayed or we removed load.
*
* Since both these conditions indicate a changed cfs_rq->avg.load we should
* call update_tg_load_avg() when this function returns true.
*/
static inline int
update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
{
unsigned long removed_load = 0, removed_util = 0, removed_runnable = 0;
struct sched_avg *sa = &cfs_rq->avg;
int decayed = 0;
if (cfs_rq->removed.nr) {
unsigned long r;
u32 divider = get_pelt_divider(&cfs_rq->avg);
raw_spin_lock(&cfs_rq->removed.lock);
swap(cfs_rq->removed.util_avg, removed_util);
swap(cfs_rq->removed.load_avg, removed_load);
swap(cfs_rq->removed.runnable_avg, removed_runnable);
cfs_rq->removed.nr = 0;
raw_spin_unlock(&cfs_rq->removed.lock);
r = removed_load;
sub_positive(&sa->load_avg, r);
sub_positive(&sa->load_sum, r * divider);
/* See sa->util_sum below */
sa->load_sum = max_t(u32, sa->load_sum, sa->load_avg * PELT_MIN_DIVIDER);
r = removed_util;
sub_positive(&sa->util_avg, r);
sub_positive(&sa->util_sum, r * divider);
/*
* Because of rounding, se->util_sum might ends up being +1 more than
* cfs->util_sum. Although this is not a problem by itself, detaching
* a lot of tasks with the rounding problem between 2 updates of
* util_avg (~1ms) can make cfs->util_sum becoming null whereas
* cfs_util_avg is not.
* Check that util_sum is still above its lower bound for the new
* util_avg. Given that period_contrib might have moved since the last
* sync, we are only sure that util_sum must be above or equal to
* util_avg * minimum possible divider
*/
sa->util_sum = max_t(u32, sa->util_sum, sa->util_avg * PELT_MIN_DIVIDER);
r = removed_runnable;
sub_positive(&sa->runnable_avg, r);
sub_positive(&sa->runnable_sum, r * divider);
/* See sa->util_sum above */
sa->runnable_sum = max_t(u32, sa->runnable_sum,
sa->runnable_avg * PELT_MIN_DIVIDER);
/*
* removed_runnable is the unweighted version of removed_load so we
* can use it to estimate removed_load_sum.
*/
add_tg_cfs_propagate(cfs_rq,
-(long)(removed_runnable * divider) >> SCHED_CAPACITY_SHIFT);
decayed = 1;
}
decayed |= __update_load_avg_cfs_rq(now, cfs_rq);
u64_u32_store_copy(sa->last_update_time,
cfs_rq->last_update_time_copy,
sa->last_update_time);
return decayed;
}
/**
* attach_entity_load_avg - attach this entity to its cfs_rq load avg
* @cfs_rq: cfs_rq to attach to
* @se: sched_entity to attach
*
* Must call update_cfs_rq_load_avg() before this, since we rely on
* cfs_rq->avg.last_update_time being current.
*/
static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
/*
* cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
* See ___update_load_avg() for details.
*/
u32 divider = get_pelt_divider(&cfs_rq->avg);
/*
* When we attach the @se to the @cfs_rq, we must align the decay
* window because without that, really weird and wonderful things can
* happen.
*
* XXX illustrate
*/
se->avg.last_update_time = cfs_rq->avg.last_update_time;
se->avg.period_contrib = cfs_rq->avg.period_contrib;
/*
* Hell(o) Nasty stuff.. we need to recompute _sum based on the new
* period_contrib. This isn't strictly correct, but since we're
* entirely outside of the PELT hierarchy, nobody cares if we truncate
* _sum a little.
*/
se->avg.util_sum = se->avg.util_avg * divider;
se->avg.runnable_sum = se->avg.runnable_avg * divider;
se->avg.load_sum = se->avg.load_avg * divider;
if (se_weight(se) < se->avg.load_sum)
se->avg.load_sum = div_u64(se->avg.load_sum, se_weight(se));
else
se->avg.load_sum = 1;
enqueue_load_avg(cfs_rq, se);
cfs_rq->avg.util_avg += se->avg.util_avg;
cfs_rq->avg.util_sum += se->avg.util_sum;
cfs_rq->avg.runnable_avg += se->avg.runnable_avg;
cfs_rq->avg.runnable_sum += se->avg.runnable_sum;
add_tg_cfs_propagate(cfs_rq, se->avg.load_sum);
cfs_rq_util_change(cfs_rq, 0);
trace_pelt_cfs_tp(cfs_rq);
}
/**
* detach_entity_load_avg - detach this entity from its cfs_rq load avg
* @cfs_rq: cfs_rq to detach from
* @se: sched_entity to detach
*
* Must call update_cfs_rq_load_avg() before this, since we rely on
* cfs_rq->avg.last_update_time being current.
*/
static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
dequeue_load_avg(cfs_rq, se);
sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
/* See update_cfs_rq_load_avg() */
cfs_rq->avg.util_sum = max_t(u32, cfs_rq->avg.util_sum,
cfs_rq->avg.util_avg * PELT_MIN_DIVIDER);
sub_positive(&cfs_rq->avg.runnable_avg, se->avg.runnable_avg);
sub_positive(&cfs_rq->avg.runnable_sum, se->avg.runnable_sum);
/* See update_cfs_rq_load_avg() */
cfs_rq->avg.runnable_sum = max_t(u32, cfs_rq->avg.runnable_sum,
cfs_rq->avg.runnable_avg * PELT_MIN_DIVIDER);
add_tg_cfs_propagate(cfs_rq, -se->avg.load_sum);
cfs_rq_util_change(cfs_rq, 0);
trace_pelt_cfs_tp(cfs_rq);
}
/*
* Optional action to be done while updating the load average
*/
#define UPDATE_TG 0x1
#define SKIP_AGE_LOAD 0x2
#define DO_ATTACH 0x4
#define DO_DETACH 0x8
/* Update task and its cfs_rq load average */
static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
u64 now = cfs_rq_clock_pelt(cfs_rq);
int decayed;
/*
* Track task load average for carrying it to new CPU after migrated, and
* track group sched_entity load average for task_h_load calc in migration
*/
if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD))
__update_load_avg_se(now, cfs_rq, se);
decayed = update_cfs_rq_load_avg(now, cfs_rq);
decayed |= propagate_entity_load_avg(se);
if (!se->avg.last_update_time && (flags & DO_ATTACH)) {
/*
* DO_ATTACH means we're here from enqueue_entity().
* !last_update_time means we've passed through
* migrate_task_rq_fair() indicating we migrated.
*
* IOW we're enqueueing a task on a new CPU.
*/
attach_entity_load_avg(cfs_rq, se);
update_tg_load_avg(cfs_rq);
} else if (flags & DO_DETACH) {
/*
* DO_DETACH means we're here from dequeue_entity()
* and we are migrating task out of the CPU.
*/
detach_entity_load_avg(cfs_rq, se);
update_tg_load_avg(cfs_rq);
} else if (decayed) {
cfs_rq_util_change(cfs_rq, 0);
if (flags & UPDATE_TG)
update_tg_load_avg(cfs_rq);
}
}
/*
* Synchronize entity load avg of dequeued entity without locking
* the previous rq.
*/
static void sync_entity_load_avg(struct sched_entity *se)
{
struct cfs_rq *cfs_rq = cfs_rq_of(se);
u64 last_update_time;
last_update_time = cfs_rq_last_update_time(cfs_rq);
__update_load_avg_blocked_se(last_update_time, se);
}
/*
* Task first catches up with cfs_rq, and then subtract
* itself from the cfs_rq (task must be off the queue now).
*/
static void remove_entity_load_avg(struct sched_entity *se)
{
struct cfs_rq *cfs_rq = cfs_rq_of(se);
unsigned long flags;
/*
* tasks cannot exit without having gone through wake_up_new_task() ->
* enqueue_task_fair() which will have added things to the cfs_rq,
* so we can remove unconditionally.
*/
sync_entity_load_avg(se);
raw_spin_lock_irqsave(&cfs_rq->removed.lock, flags);
++cfs_rq->removed.nr;
cfs_rq->removed.util_avg += se->avg.util_avg;
cfs_rq->removed.load_avg += se->avg.load_avg;
cfs_rq->removed.runnable_avg += se->avg.runnable_avg;
raw_spin_unlock_irqrestore(&cfs_rq->removed.lock, flags);
}
static inline unsigned long cfs_rq_runnable_avg(struct cfs_rq *cfs_rq)
{
return cfs_rq->avg.runnable_avg;
}
static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
{
return cfs_rq->avg.load_avg;
}
static int newidle_balance(struct rq *this_rq, struct rq_flags *rf);
static inline unsigned long task_util(struct task_struct *p)
{
return READ_ONCE(p->se.avg.util_avg);
}
static inline unsigned long _task_util_est(struct task_struct *p)
{
struct util_est ue = READ_ONCE(p->se.avg.util_est);
return max(ue.ewma, (ue.enqueued & ~UTIL_AVG_UNCHANGED));
}
static inline unsigned long task_util_est(struct task_struct *p)
{
return max(task_util(p), _task_util_est(p));
}
#ifdef CONFIG_UCLAMP_TASK
static inline unsigned long uclamp_task_util(struct task_struct *p,
unsigned long uclamp_min,
unsigned long uclamp_max)
{
return clamp(task_util_est(p), uclamp_min, uclamp_max);
}
#else
static inline unsigned long uclamp_task_util(struct task_struct *p,
unsigned long uclamp_min,
unsigned long uclamp_max)
{
return task_util_est(p);
}
#endif
static inline void util_est_enqueue(struct cfs_rq *cfs_rq,
struct task_struct *p)
{
unsigned int enqueued;
if (!sched_feat(UTIL_EST))
return;
/* Update root cfs_rq's estimated utilization */
enqueued = cfs_rq->avg.util_est.enqueued;
enqueued += _task_util_est(p);
WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued);
trace_sched_util_est_cfs_tp(cfs_rq);
}
static inline void util_est_dequeue(struct cfs_rq *cfs_rq,
struct task_struct *p)
{
unsigned int enqueued;
if (!sched_feat(UTIL_EST))
return;
/* Update root cfs_rq's estimated utilization */
enqueued = cfs_rq->avg.util_est.enqueued;
enqueued -= min_t(unsigned int, enqueued, _task_util_est(p));
WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued);
trace_sched_util_est_cfs_tp(cfs_rq);
}
#define UTIL_EST_MARGIN (SCHED_CAPACITY_SCALE / 100)
/*
* Check if a (signed) value is within a specified (unsigned) margin,
* based on the observation that:
*
* abs(x) < y := (unsigned)(x + y - 1) < (2 * y - 1)
*
* NOTE: this only works when value + margin < INT_MAX.
*/
static inline bool within_margin(int value, int margin)
{
return ((unsigned int)(value + margin - 1) < (2 * margin - 1));
}
static inline void util_est_update(struct cfs_rq *cfs_rq,
struct task_struct *p,
bool task_sleep)
{
long last_ewma_diff, last_enqueued_diff;
struct util_est ue;
if (!sched_feat(UTIL_EST))
return;
/*
* Skip update of task's estimated utilization when the task has not
* yet completed an activation, e.g. being migrated.
*/
if (!task_sleep)
return;
/*
* If the PELT values haven't changed since enqueue time,
* skip the util_est update.
*/
ue = p->se.avg.util_est;
if (ue.enqueued & UTIL_AVG_UNCHANGED)
return;
last_enqueued_diff = ue.enqueued;
/*
* Reset EWMA on utilization increases, the moving average is used only
* to smooth utilization decreases.
*/
ue.enqueued = task_util(p);
if (sched_feat(UTIL_EST_FASTUP)) {
if (ue.ewma < ue.enqueued) {
ue.ewma = ue.enqueued;
goto done;
}
}
/*
* Skip update of task's estimated utilization when its members are
* already ~1% close to its last activation value.
*/
last_ewma_diff = ue.enqueued - ue.ewma;
last_enqueued_diff -= ue.enqueued;
if (within_margin(last_ewma_diff, UTIL_EST_MARGIN)) {
if (!within_margin(last_enqueued_diff, UTIL_EST_MARGIN))
goto done;
return;
}
/*
* To avoid overestimation of actual task utilization, skip updates if
* we cannot grant there is idle time in this CPU.
*/
if (task_util(p) > capacity_orig_of(cpu_of(rq_of(cfs_rq))))
return;
/*
* Update Task's estimated utilization
*
* When *p completes an activation we can consolidate another sample
* of the task size. This is done by storing the current PELT value
* as ue.enqueued and by using this value to update the Exponential
* Weighted Moving Average (EWMA):
*
* ewma(t) = w * task_util(p) + (1-w) * ewma(t-1)
* = w * task_util(p) + ewma(t-1) - w * ewma(t-1)
* = w * (task_util(p) - ewma(t-1)) + ewma(t-1)
* = w * ( last_ewma_diff ) + ewma(t-1)
* = w * (last_ewma_diff + ewma(t-1) / w)
*
* Where 'w' is the weight of new samples, which is configured to be
* 0.25, thus making w=1/4 ( >>= UTIL_EST_WEIGHT_SHIFT)
*/
ue.ewma <<= UTIL_EST_WEIGHT_SHIFT;
ue.ewma += last_ewma_diff;
ue.ewma >>= UTIL_EST_WEIGHT_SHIFT;
done:
ue.enqueued |= UTIL_AVG_UNCHANGED;
WRITE_ONCE(p->se.avg.util_est, ue);
trace_sched_util_est_se_tp(&p->se);
}
static inline int util_fits_cpu(unsigned long util,
unsigned long uclamp_min,
unsigned long uclamp_max,
int cpu)
{
unsigned long capacity_orig, capacity_orig_thermal;
unsigned long capacity = capacity_of(cpu);
bool fits, uclamp_max_fits;
/*
* Check if the real util fits without any uclamp boost/cap applied.
*/
fits = fits_capacity(util, capacity);
if (!uclamp_is_used())
return fits;
/*
* We must use capacity_orig_of() for comparing against uclamp_min and
* uclamp_max. We only care about capacity pressure (by using
* capacity_of()) for comparing against the real util.
*
* If a task is boosted to 1024 for example, we don't want a tiny
* pressure to skew the check whether it fits a CPU or not.
*
* Similarly if a task is capped to capacity_orig_of(little_cpu), it
* should fit a little cpu even if there's some pressure.
*
* Only exception is for thermal pressure since it has a direct impact
* on available OPP of the system.
*
* We honour it for uclamp_min only as a drop in performance level
* could result in not getting the requested minimum performance level.
*
* For uclamp_max, we can tolerate a drop in performance level as the
* goal is to cap the task. So it's okay if it's getting less.
*/
capacity_orig = capacity_orig_of(cpu);
capacity_orig_thermal = capacity_orig - arch_scale_thermal_pressure(cpu);
/*
* We want to force a task to fit a cpu as implied by uclamp_max.
* But we do have some corner cases to cater for..
*
*
* C=z
* | ___
* | C=y | |
* |_ _ _ _ _ _ _ _ _ ___ _ _ _ | _ | _ _ _ _ _ uclamp_max
* | C=x | | | |
* | ___ | | | |
* | | | | | | | (util somewhere in this region)
* | | | | | | |
* | | | | | | |
* +----------------------------------------
* cpu0 cpu1 cpu2
*
* In the above example if a task is capped to a specific performance
* point, y, then when:
*
* * util = 80% of x then it does not fit on cpu0 and should migrate
* to cpu1
* * util = 80% of y then it is forced to fit on cpu1 to honour
* uclamp_max request.
*
* which is what we're enforcing here. A task always fits if
* uclamp_max <= capacity_orig. But when uclamp_max > capacity_orig,
* the normal upmigration rules should withhold still.
*
* Only exception is when we are on max capacity, then we need to be
* careful not to block overutilized state. This is so because:
*
* 1. There's no concept of capping at max_capacity! We can't go
* beyond this performance level anyway.
* 2. The system is being saturated when we're operating near
* max capacity, it doesn't make sense to block overutilized.
*/
uclamp_max_fits = (capacity_orig == SCHED_CAPACITY_SCALE) && (uclamp_max == SCHED_CAPACITY_SCALE);
uclamp_max_fits = !uclamp_max_fits && (uclamp_max <= capacity_orig);
fits = fits || uclamp_max_fits;
/*
*
* C=z
* | ___ (region a, capped, util >= uclamp_max)
* | C=y | |
* |_ _ _ _ _ _ _ _ _ ___ _ _ _ | _ | _ _ _ _ _ uclamp_max
* | C=x | | | |
* | ___ | | | | (region b, uclamp_min <= util <= uclamp_max)
* |_ _ _|_ _|_ _ _ _| _ | _ _ _| _ | _ _ _ _ _ uclamp_min
* | | | | | | |
* | | | | | | | (region c, boosted, util < uclamp_min)
* +----------------------------------------
* cpu0 cpu1 cpu2
*
* a) If util > uclamp_max, then we're capped, we don't care about
* actual fitness value here. We only care if uclamp_max fits
* capacity without taking margin/pressure into account.
* See comment above.
*
* b) If uclamp_min <= util <= uclamp_max, then the normal
* fits_capacity() rules apply. Except we need to ensure that we
* enforce we remain within uclamp_max, see comment above.
*
* c) If util < uclamp_min, then we are boosted. Same as (b) but we
* need to take into account the boosted value fits the CPU without
* taking margin/pressure into account.
*
* Cases (a) and (b) are handled in the 'fits' variable already. We
* just need to consider an extra check for case (c) after ensuring we
* handle the case uclamp_min > uclamp_max.
*/
uclamp_min = min(uclamp_min, uclamp_max);
if (fits && (util < uclamp_min) && (uclamp_min > capacity_orig_thermal))
return -1;
return fits;
}
static inline int task_fits_cpu(struct task_struct *p, int cpu)
{
unsigned long uclamp_min = uclamp_eff_value(p, UCLAMP_MIN);
unsigned long uclamp_max = uclamp_eff_value(p, UCLAMP_MAX);
unsigned long util = task_util_est(p);
/*
* Return true only if the cpu fully fits the task requirements, which
* include the utilization but also the performance hints.
*/
return (util_fits_cpu(util, uclamp_min, uclamp_max, cpu) > 0);
}
static inline void update_misfit_status(struct task_struct *p, struct rq *rq)
{
if (!sched_asym_cpucap_active())
return;
if (!p || p->nr_cpus_allowed == 1) {
rq->misfit_task_load = 0;
return;
}
if (task_fits_cpu(p, cpu_of(rq))) {
rq->misfit_task_load = 0;
return;
}
/*
* Make sure that misfit_task_load will not be null even if
* task_h_load() returns 0.
*/
rq->misfit_task_load = max_t(unsigned long, task_h_load(p), 1);
}
#else /* CONFIG_SMP */
static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
{
return true;
}
#define UPDATE_TG 0x0
#define SKIP_AGE_LOAD 0x0
#define DO_ATTACH 0x0
#define DO_DETACH 0x0
static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1)
{
cfs_rq_util_change(cfs_rq, 0);
}
static inline void remove_entity_load_avg(struct sched_entity *se) {}
static inline void
attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
static inline void
detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
static inline int newidle_balance(struct rq *rq, struct rq_flags *rf)
{
return 0;
}
static inline void
util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p) {}
static inline void
util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p) {}
static inline void
util_est_update(struct cfs_rq *cfs_rq, struct task_struct *p,
bool task_sleep) {}
static inline void update_misfit_status(struct task_struct *p, struct rq *rq) {}
#endif /* CONFIG_SMP */
static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
#ifdef CONFIG_SCHED_DEBUG
s64 d = se->vruntime - cfs_rq->min_vruntime;
if (d < 0)
d = -d;
if (d > 3*sysctl_sched_latency)
schedstat_inc(cfs_rq->nr_spread_over);
#endif
}
static inline bool entity_is_long_sleeper(struct sched_entity *se)
{
struct cfs_rq *cfs_rq;
u64 sleep_time;
if (se->exec_start == 0)
return false;
cfs_rq = cfs_rq_of(se);
sleep_time = rq_clock_task(rq_of(cfs_rq));
/* Happen while migrating because of clock task divergence */
if (sleep_time <= se->exec_start)
return false;
sleep_time -= se->exec_start;
if (sleep_time > ((1ULL << 63) / scale_load_down(NICE_0_LOAD)))
return true;
return false;
}
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
u64 vruntime = cfs_rq->min_vruntime;
/*
* The 'current' period is already promised to the current tasks,
* however the extra weight of the new task will slow them down a
* little, place the new task so that it fits in the slot that
* stays open at the end.
*/
if (initial && sched_feat(START_DEBIT))
vruntime += sched_vslice(cfs_rq, se);
/* sleeps up to a single latency don't count. */
if (!initial) {
unsigned long thresh;
if (se_is_idle(se))
thresh = sysctl_sched_min_granularity;
else
thresh = sysctl_sched_latency;
/*
* Halve their sleep time's effect, to allow
* for a gentler effect of sleepers:
*/
if (sched_feat(GENTLE_FAIR_SLEEPERS))
thresh >>= 1;
vruntime -= thresh;
}
/*
* Pull vruntime of the entity being placed to the base level of
* cfs_rq, to prevent boosting it if placed backwards.
* However, min_vruntime can advance much faster than real time, with
* the extreme being when an entity with the minimal weight always runs
* on the cfs_rq. If the waking entity slept for a long time, its
* vruntime difference from min_vruntime may overflow s64 and their
* comparison may get inversed, so ignore the entity's original
* vruntime in that case.
* The maximal vruntime speedup is given by the ratio of normal to
* minimal weight: scale_load_down(NICE_0_LOAD) / MIN_SHARES.
* When placing a migrated waking entity, its exec_start has been set
* from a different rq. In order to take into account a possible
* divergence between new and prev rq's clocks task because of irq and
* stolen time, we take an additional margin.
* So, cutting off on the sleep time of
* 2^63 / scale_load_down(NICE_0_LOAD) ~ 104 days
* should be safe.
*/
if (entity_is_long_sleeper(se))
se->vruntime = vruntime;
else
se->vruntime = max_vruntime(se->vruntime, vruntime);
}
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
static inline bool cfs_bandwidth_used(void);
/*
* MIGRATION
*
* dequeue
* update_curr()
* update_min_vruntime()
* vruntime -= min_vruntime
*
* enqueue
* update_curr()
* update_min_vruntime()
* vruntime += min_vruntime
*
* this way the vruntime transition between RQs is done when both
* min_vruntime are up-to-date.
*
* WAKEUP (remote)
*
* ->migrate_task_rq_fair() (p->state == TASK_WAKING)
* vruntime -= min_vruntime
*
* enqueue
* update_curr()
* update_min_vruntime()
* vruntime += min_vruntime
*
* this way we don't have the most up-to-date min_vruntime on the originating
* CPU and an up-to-date min_vruntime on the destination CPU.
*/
static void
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
bool curr = cfs_rq->curr == se;
/*
* If we're the current task, we must renormalise before calling
* update_curr().
*/
if (renorm && curr)
se->vruntime += cfs_rq->min_vruntime;
update_curr(cfs_rq);
/*
* Otherwise, renormalise after, such that we're placed at the current
* moment in time, instead of some random moment in the past. Being
* placed in the past could significantly boost this task to the
* fairness detriment of existing tasks.
*/
if (renorm && !curr)
se->vruntime += cfs_rq->min_vruntime;
/*
* When enqueuing a sched_entity, we must:
* - Update loads to have both entity and cfs_rq synced with now.
* - For group_entity, update its runnable_weight to reflect the new
* h_nr_running of its group cfs_rq.
* - For group_entity, update its weight to reflect the new share of
* its group cfs_rq
* - Add its new weight to cfs_rq->load.weight
*/
update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
se_update_runnable(se);
update_cfs_group(se);
account_entity_enqueue(cfs_rq, se);
if (flags & ENQUEUE_WAKEUP)
place_entity(cfs_rq, se, 0);
/* Entity has migrated, no longer consider this task hot */
if (flags & ENQUEUE_MIGRATED)
se->exec_start = 0;
check_schedstat_required();
update_stats_enqueue_fair(cfs_rq, se, flags);
check_spread(cfs_rq, se);
if (!curr)
__enqueue_entity(cfs_rq, se);
se->on_rq = 1;
if (cfs_rq->nr_running == 1) {
check_enqueue_throttle(cfs_rq);
if (!throttled_hierarchy(cfs_rq))
list_add_leaf_cfs_rq(cfs_rq);
}
}
static void __clear_buddies_last(struct sched_entity *se)
{
for_each_sched_entity(se) {
struct cfs_rq *cfs_rq = cfs_rq_of(se);
if (cfs_rq->last != se)
break;
cfs_rq->last = NULL;
}
}
static void __clear_buddies_next(struct sched_entity *se)
{
for_each_sched_entity(se) {
struct cfs_rq *cfs_rq = cfs_rq_of(se);
if (cfs_rq->next != se)
break;
cfs_rq->next = NULL;
}
}
static void __clear_buddies_skip(struct sched_entity *se)
{
for_each_sched_entity(se) {
struct cfs_rq *cfs_rq = cfs_rq_of(se);
if (cfs_rq->skip != se)
break;
cfs_rq->skip = NULL;
}
}
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
if (cfs_rq->last == se)
__clear_buddies_last(se);
if (cfs_rq->next == se)
__clear_buddies_next(se);
if (cfs_rq->skip == se)
__clear_buddies_skip(se);
}
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
static void
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
int action = UPDATE_TG;
if (entity_is_task(se) && task_on_rq_migrating(task_of(se)))
action |= DO_DETACH;
/*
* Update run-time statistics of the 'current'.
*/
update_curr(cfs_rq);
/*
* When dequeuing a sched_entity, we must:
* - Update loads to have both entity and cfs_rq synced with now.
* - For group_entity, update its runnable_weight to reflect the new
* h_nr_running of its group cfs_rq.
* - Subtract its previous weight from cfs_rq->load.weight.
* - For group entity, update its weight to reflect the new share
* of its group cfs_rq.
*/
update_load_avg(cfs_rq, se, action);
se_update_runnable(se);
update_stats_dequeue_fair(cfs_rq, se, flags);
clear_buddies(cfs_rq, se);
if (se != cfs_rq->curr)
__dequeue_entity(cfs_rq, se);
se->on_rq = 0;
account_entity_dequeue(cfs_rq, se);
/*
* Normalize after update_curr(); which will also have moved
* min_vruntime if @se is the one holding it back. But before doing
* update_min_vruntime() again, which will discount @se's position and
* can move min_vruntime forward still more.
*/
if (!(flags & DEQUEUE_SLEEP))
se->vruntime -= cfs_rq->min_vruntime;
/* return excess runtime on last dequeue */
return_cfs_rq_runtime(cfs_rq);
update_cfs_group(se);
/*
* Now advance min_vruntime if @se was the entity holding it back,
* except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be
* put back on, and if we advance min_vruntime, we'll be placed back
* further than we started -- ie. we'll be penalized.
*/
if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) != DEQUEUE_SAVE)
update_min_vruntime(cfs_rq);
if (cfs_rq->nr_running == 0)
update_idle_cfs_rq_clock_pelt(cfs_rq);
}
/*
* Preempt the current task with a newly woken task if needed:
*/
static void
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
{
unsigned long ideal_runtime, delta_exec;
struct sched_entity *se;
s64 delta;
/*
* When many tasks blow up the sched_period; it is possible that
* sched_slice() reports unusually large results (when many tasks are
* very light for example). Therefore impose a maximum.
*/
ideal_runtime = min_t(u64, sched_slice(cfs_rq, curr), sysctl_sched_latency);
delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
if (delta_exec > ideal_runtime) {
resched_curr(rq_of(cfs_rq));
/*
* The current task ran long enough, ensure it doesn't get
* re-elected due to buddy favours.
*/
clear_buddies(cfs_rq, curr);
return;
}
/*
* Ensure that a task that missed wakeup preemption by a
* narrow margin doesn't have to wait for a full slice.
* This also mitigates buddy induced latencies under load.
*/
if (delta_exec < sysctl_sched_min_granularity)
return;
se = __pick_first_entity(cfs_rq);
delta = curr->vruntime - se->vruntime;
if (delta < 0)
return;
if (delta > ideal_runtime)
resched_curr(rq_of(cfs_rq));
}
static void
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
clear_buddies(cfs_rq, se);
/* 'current' is not kept within the tree. */
if (se->on_rq) {
/*
* Any task has to be enqueued before it get to execute on
* a CPU. So account for the time it spent waiting on the
* runqueue.
*/
update_stats_wait_end_fair(cfs_rq, se);
__dequeue_entity(cfs_rq, se);
update_load_avg(cfs_rq, se, UPDATE_TG);
}
update_stats_curr_start(cfs_rq, se);
cfs_rq->curr = se;
/*
* Track our maximum slice length, if the CPU's load is at
* least twice that of our own weight (i.e. dont track it
* when there are only lesser-weight tasks around):
*/
if (schedstat_enabled() &&
rq_of(cfs_rq)->cfs.load.weight >= 2*se->load.weight) {
struct sched_statistics *stats;
stats = __schedstats_from_se(se);
__schedstat_set(stats->slice_max,
max((u64)stats->slice_max,
se->sum_exec_runtime - se->prev_sum_exec_runtime));
}
se->prev_sum_exec_runtime = se->sum_exec_runtime;
}
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
/*
* Pick the next process, keeping these things in mind, in this order:
* 1) keep things fair between processes/task groups
* 2) pick the "next" process, since someone really wants that to run
* 3) pick the "last" process, for cache locality
* 4) do not run the "skip" process, if something else is available
*/
static struct sched_entity *
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
{
struct sched_entity *left = __pick_first_entity(cfs_rq);
struct sched_entity *se;
/*
* If curr is set we have to see if its left of the leftmost entity
* still in the tree, provided there was anything in the tree at all.
*/
if (!left || (curr && entity_before(curr, left)))
left = curr;
se = left; /* ideally we run the leftmost entity */
/*
* Avoid running the skip buddy, if running something else can
* be done without getting too unfair.
*/
if (cfs_rq->skip && cfs_rq->skip == se) {
struct sched_entity *second;
if (se == curr) {
second = __pick_first_entity(cfs_rq);
} else {
second = __pick_next_entity(se);
if (!second || (curr && entity_before(curr, second)))
second = curr;
}
if (second && wakeup_preempt_entity(second, left) < 1)
se = second;
}
if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) {
/*
* Someone really wants this to run. If it's not unfair, run it.
*/
se = cfs_rq->next;
} else if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1) {
/*
* Prefer last buddy, try to return the CPU to a preempted task.
*/
se = cfs_rq->last;
}
return se;
}
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
{
/*
* If still on the runqueue then deactivate_task()
* was not called and update_curr() has to be done:
*/
if (prev->on_rq)
update_curr(cfs_rq);
/* throttle cfs_rqs exceeding runtime */
check_cfs_rq_runtime(cfs_rq);
check_spread(cfs_rq, prev);
if (prev->on_rq) {
update_stats_wait_start_fair(cfs_rq, prev);
/* Put 'current' back into the tree. */
__enqueue_entity(cfs_rq, prev);
/* in !on_rq case, update occurred at dequeue */
update_load_avg(cfs_rq, prev, 0);
}
cfs_rq->curr = NULL;
}
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
{
/*
* Update run-time statistics of the 'current'.
*/
update_curr(cfs_rq);
/*
* Ensure that runnable average is periodically updated.
*/
update_load_avg(cfs_rq, curr, UPDATE_TG);
update_cfs_group(curr);
#ifdef CONFIG_SCHED_HRTICK
/*
* queued ticks are scheduled to match the slice, so don't bother
* validating it and just reschedule.
*/
if (queued) {
resched_curr(rq_of(cfs_rq));
return;
}
/*
* don't let the period tick interfere with the hrtick preemption
*/
if (!sched_feat(DOUBLE_TICK) &&
hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
return;
#endif
if (cfs_rq->nr_running > 1)
check_preempt_tick(cfs_rq, curr);
}
/**************************************************
* CFS bandwidth control machinery
*/
#ifdef CONFIG_CFS_BANDWIDTH
#ifdef CONFIG_JUMP_LABEL
static struct static_key __cfs_bandwidth_used;
static inline bool cfs_bandwidth_used(void)
{
return static_key_false(&__cfs_bandwidth_used);
}
void cfs_bandwidth_usage_inc(void)
{
static_key_slow_inc_cpuslocked(&__cfs_bandwidth_used);
}
void cfs_bandwidth_usage_dec(void)
{
static_key_slow_dec_cpuslocked(&__cfs_bandwidth_used);
}
#else /* CONFIG_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
return true;
}
void cfs_bandwidth_usage_inc(void) {}
void cfs_bandwidth_usage_dec(void) {}
#endif /* CONFIG_JUMP_LABEL */
/*
* default period for cfs group bandwidth.
* default: 0.1s, units: nanoseconds
*/
static inline u64 default_cfs_period(void)
{
return 100000000ULL;
}
static inline u64 sched_cfs_bandwidth_slice(void)
{
return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
}
/*
* Replenish runtime according to assigned quota. We use sched_clock_cpu
* directly instead of rq->clock to avoid adding additional synchronization
* around rq->lock.
*
* requires cfs_b->lock
*/
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
{
s64 runtime;
if (unlikely(cfs_b->quota == RUNTIME_INF))
return;
cfs_b->runtime += cfs_b->quota;
runtime = cfs_b->runtime_snap - cfs_b->runtime;
if (runtime > 0) {
cfs_b->burst_time += runtime;
cfs_b->nr_burst++;
}
cfs_b->runtime = min(cfs_b->runtime, cfs_b->quota + cfs_b->burst);
cfs_b->runtime_snap = cfs_b->runtime;
}
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
return &tg->cfs_bandwidth;
}
/* returns 0 on failure to allocate runtime */
static int __assign_cfs_rq_runtime(struct cfs_bandwidth *cfs_b,
struct cfs_rq *cfs_rq, u64 target_runtime)
{
u64 min_amount, amount = 0;
lockdep_assert_held(&cfs_b->lock);
/* note: this is a positive sum as runtime_remaining <= 0 */
min_amount = target_runtime - cfs_rq->runtime_remaining;
if (cfs_b->quota == RUNTIME_INF)
amount = min_amount;
else {
start_cfs_bandwidth(cfs_b);
if (cfs_b->runtime > 0) {
amount = min(cfs_b->runtime, min_amount);
cfs_b->runtime -= amount;
cfs_b->idle = 0;
}
}
cfs_rq->runtime_remaining += amount;
return cfs_rq->runtime_remaining > 0;
}
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
int ret;
raw_spin_lock(&cfs_b->lock);
ret = __assign_cfs_rq_runtime(cfs_b, cfs_rq, sched_cfs_bandwidth_slice());
raw_spin_unlock(&cfs_b->lock);
return ret;
}
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
{
/* dock delta_exec before expiring quota (as it could span periods) */
cfs_rq->runtime_remaining -= delta_exec;
if (likely(cfs_rq->runtime_remaining > 0))
return;
if (cfs_rq->throttled)
return;
/*
* if we're unable to extend our runtime we resched so that the active
* hierarchy can be throttled
*/
if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
resched_curr(rq_of(cfs_rq));
}
static __always_inline
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
{
if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
return;
__account_cfs_rq_runtime(cfs_rq, delta_exec);
}
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
return cfs_bandwidth_used() && cfs_rq->throttled;
}
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
return cfs_bandwidth_used() && cfs_rq->throttle_count;
}
/*
* Ensure that neither of the group entities corresponding to src_cpu or
* dest_cpu are members of a throttled hierarchy when performing group
* load-balance operations.
*/
static inline int throttled_lb_pair(struct task_group *tg,
int src_cpu, int dest_cpu)
{
struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
src_cfs_rq = tg->cfs_rq[src_cpu];
dest_cfs_rq = tg->cfs_rq[dest_cpu];
return throttled_hierarchy(src_cfs_rq) ||
throttled_hierarchy(dest_cfs_rq);
}
static int tg_unthrottle_up(struct task_group *tg, void *data)
{
struct rq *rq = data;
struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
cfs_rq->throttle_count--;
if (!cfs_rq->throttle_count) {
cfs_rq->throttled_clock_pelt_time += rq_clock_pelt(rq) -
cfs_rq->throttled_clock_pelt;
/* Add cfs_rq with load or one or more already running entities to the list */
if (!cfs_rq_is_decayed(cfs_rq))
list_add_leaf_cfs_rq(cfs_rq);
}
return 0;
}
static int tg_throttle_down(struct task_group *tg, void *data)
{
struct rq *rq = data;
struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
/* group is entering throttled state, stop time */
if (!cfs_rq->throttle_count) {
cfs_rq->throttled_clock_pelt = rq_clock_pelt(rq);
list_del_leaf_cfs_rq(cfs_rq);
}
cfs_rq->throttle_count++;
return 0;
}
static bool throttle_cfs_rq(struct cfs_rq *cfs_rq)
{
struct rq *rq = rq_of(cfs_rq);
struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
struct sched_entity *se;
long task_delta, idle_task_delta, dequeue = 1;
raw_spin_lock(&cfs_b->lock);
/* This will start the period timer if necessary */
if (__assign_cfs_rq_runtime(cfs_b, cfs_rq, 1)) {
/*
* We have raced with bandwidth becoming available, and if we
* actually throttled the timer might not unthrottle us for an
* entire period. We additionally needed to make sure that any
* subsequent check_cfs_rq_runtime calls agree not to throttle
* us, as we may commit to do cfs put_prev+pick_next, so we ask
* for 1ns of runtime rather than just check cfs_b.
*/
dequeue = 0;
} else {
list_add_tail_rcu(&cfs_rq->throttled_list,
&cfs_b->throttled_cfs_rq);
}
raw_spin_unlock(&cfs_b->lock);
if (!dequeue)
return false; /* Throttle no longer required. */
se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
/* freeze hierarchy runnable averages while throttled */
rcu_read_lock();
walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
rcu_read_unlock();
task_delta = cfs_rq->h_nr_running;
idle_task_delta = cfs_rq->idle_h_nr_running;
for_each_sched_entity(se) {
struct cfs_rq *qcfs_rq = cfs_rq_of(se);
/* throttled entity or throttle-on-deactivate */
if (!se->on_rq)
goto done;
dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
if (cfs_rq_is_idle(group_cfs_rq(se)))
idle_task_delta = cfs_rq->h_nr_running;
qcfs_rq->h_nr_running -= task_delta;
qcfs_rq->idle_h_nr_running -= idle_task_delta;
if (qcfs_rq->load.weight) {
/* Avoid re-evaluating load for this entity: */
se = parent_entity(se);
break;
}
}
for_each_sched_entity(se) {
struct cfs_rq *qcfs_rq = cfs_rq_of(se);
/* throttled entity or throttle-on-deactivate */
if (!se->on_rq)
goto done;
update_load_avg(qcfs_rq, se, 0);
se_update_runnable(se);
if (cfs_rq_is_idle(group_cfs_rq(se)))
idle_task_delta = cfs_rq->h_nr_running;
qcfs_rq->h_nr_running -= task_delta;
qcfs_rq->idle_h_nr_running -= idle_task_delta;
}
/* At this point se is NULL and we are at root level*/
sub_nr_running(rq, task_delta);
done:
/*
* Note: distribution will already see us throttled via the
* throttled-list. rq->lock protects completion.
*/
cfs_rq->throttled = 1;
cfs_rq->throttled_clock = rq_clock(rq);
return true;
}
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
{
struct rq *rq = rq_of(cfs_rq);
struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
struct sched_entity *se;
long task_delta, idle_task_delta;
se = cfs_rq->tg->se[cpu_of(rq)];
cfs_rq->throttled = 0;
update_rq_clock(rq);
raw_spin_lock(&cfs_b->lock);
cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
list_del_rcu(&cfs_rq->throttled_list);
raw_spin_unlock(&cfs_b->lock);
/* update hierarchical throttle state */
walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
if (!cfs_rq->load.weight) {
if (!cfs_rq->on_list)
return;
/*
* Nothing to run but something to decay (on_list)?
* Complete the branch.
*/
for_each_sched_entity(se) {
if (list_add_leaf_cfs_rq(cfs_rq_of(se)))
break;
}
goto unthrottle_throttle;
}
task_delta = cfs_rq->h_nr_running;
idle_task_delta = cfs_rq->idle_h_nr_running;
for_each_sched_entity(se) {
struct cfs_rq *qcfs_rq = cfs_rq_of(se);
if (se->on_rq)
break;
enqueue_entity(qcfs_rq, se, ENQUEUE_WAKEUP);
if (cfs_rq_is_idle(group_cfs_rq(se)))
idle_task_delta = cfs_rq->h_nr_running;
qcfs_rq->h_nr_running += task_delta;
qcfs_rq->idle_h_nr_running += idle_task_delta;
/* end evaluation on encountering a throttled cfs_rq */
if (cfs_rq_throttled(qcfs_rq))
goto unthrottle_throttle;
}
for_each_sched_entity(se) {
struct cfs_rq *qcfs_rq = cfs_rq_of(se);
update_load_avg(qcfs_rq, se, UPDATE_TG);
se_update_runnable(se);
if (cfs_rq_is_idle(group_cfs_rq(se)))
idle_task_delta = cfs_rq->h_nr_running;
qcfs_rq->h_nr_running += task_delta;
qcfs_rq->idle_h_nr_running += idle_task_delta;
/* end evaluation on encountering a throttled cfs_rq */
if (cfs_rq_throttled(qcfs_rq))
goto unthrottle_throttle;
}
/* At this point se is NULL and we are at root level*/
add_nr_running(rq, task_delta);
unthrottle_throttle:
assert_list_leaf_cfs_rq(rq);
/* Determine whether we need to wake up potentially idle CPU: */
if (rq->curr == rq->idle && rq->cfs.nr_running)
resched_curr(rq);
}
#ifdef CONFIG_SMP
static void __cfsb_csd_unthrottle(void *arg)
{
struct cfs_rq *cursor, *tmp;
struct rq *rq = arg;
struct rq_flags rf;
rq_lock(rq, &rf);
/*
* Iterating over the list can trigger several call to
* update_rq_clock() in unthrottle_cfs_rq().
* Do it once and skip the potential next ones.
*/
update_rq_clock(rq);
rq_clock_start_loop_update(rq);
/*
* Since we hold rq lock we're safe from concurrent manipulation of
* the CSD list. However, this RCU critical section annotates the
* fact that we pair with sched_free_group_rcu(), so that we cannot
* race with group being freed in the window between removing it
* from the list and advancing to the next entry in the list.
*/
rcu_read_lock();
list_for_each_entry_safe(cursor, tmp, &rq->cfsb_csd_list,
throttled_csd_list) {
list_del_init(&cursor->throttled_csd_list);
if (cfs_rq_throttled(cursor))
unthrottle_cfs_rq(cursor);
}
rcu_read_unlock();
rq_clock_stop_loop_update(rq);
rq_unlock(rq, &rf);
}
static inline void __unthrottle_cfs_rq_async(struct cfs_rq *cfs_rq)
{
struct rq *rq = rq_of(cfs_rq);
bool first;
if (rq == this_rq()) {
unthrottle_cfs_rq(cfs_rq);
return;
}
/* Already enqueued */
if (SCHED_WARN_ON(!list_empty(&cfs_rq->throttled_csd_list)))
return;
first = list_empty(&rq->cfsb_csd_list);
list_add_tail(&cfs_rq->throttled_csd_list, &rq->cfsb_csd_list);
if (first)
smp_call_function_single_async(cpu_of(rq), &rq->cfsb_csd);
}
#else
static inline void __unthrottle_cfs_rq_async(struct cfs_rq *cfs_rq)
{
unthrottle_cfs_rq(cfs_rq);
}
#endif
static void unthrottle_cfs_rq_async(struct cfs_rq *cfs_rq)
{
lockdep_assert_rq_held(rq_of(cfs_rq));
if (SCHED_WARN_ON(!cfs_rq_throttled(cfs_rq) ||
cfs_rq->runtime_remaining <= 0))
return;
__unthrottle_cfs_rq_async(cfs_rq);
}
static bool distribute_cfs_runtime(struct cfs_bandwidth *cfs_b)
{
struct cfs_rq *local_unthrottle = NULL;
int this_cpu = smp_processor_id();
u64 runtime, remaining = 1;
bool throttled = false;
struct cfs_rq *cfs_rq;
struct rq_flags rf;
struct rq *rq;
rcu_read_lock();
list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
throttled_list) {
rq = rq_of(cfs_rq);
if (!remaining) {
throttled = true;
break;
}
rq_lock_irqsave(rq, &rf);
if (!cfs_rq_throttled(cfs_rq))
goto next;
#ifdef CONFIG_SMP
/* Already queued for async unthrottle */
if (!list_empty(&cfs_rq->throttled_csd_list))
goto next;
#endif
/* By the above checks, this should never be true */
SCHED_WARN_ON(cfs_rq->runtime_remaining > 0);
raw_spin_lock(&cfs_b->lock);
runtime = -cfs_rq->runtime_remaining + 1;
if (runtime > cfs_b->runtime)
runtime = cfs_b->runtime;
cfs_b->runtime -= runtime;
remaining = cfs_b->runtime;
raw_spin_unlock(&cfs_b->lock);
cfs_rq->runtime_remaining += runtime;
/* we check whether we're throttled above */
if (cfs_rq->runtime_remaining > 0) {
if (cpu_of(rq) != this_cpu ||
SCHED_WARN_ON(local_unthrottle))
unthrottle_cfs_rq_async(cfs_rq);
else
local_unthrottle = cfs_rq;
} else {
throttled = true;
}
next:
rq_unlock_irqrestore(rq, &rf);
}
rcu_read_unlock();
if (local_unthrottle) {
rq = cpu_rq(this_cpu);
rq_lock_irqsave(rq, &rf);
if (cfs_rq_throttled(local_unthrottle))
unthrottle_cfs_rq(local_unthrottle);
rq_unlock_irqrestore(rq, &rf);
}
return throttled;
}
/*
* Responsible for refilling a task_group's bandwidth and unthrottling its
* cfs_rqs as appropriate. If there has been no activity within the last
* period the timer is deactivated until scheduling resumes; cfs_b->idle is
* used to track this state.
*/
static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun, unsigned long flags)
{
int throttled;
/* no need to continue the timer with no bandwidth constraint */
if (cfs_b->quota == RUNTIME_INF)
goto out_deactivate;
throttled = !list_empty(&cfs_b->throttled_cfs_rq);
cfs_b->nr_periods += overrun;
/* Refill extra burst quota even if cfs_b->idle */
__refill_cfs_bandwidth_runtime(cfs_b);
/*
* idle depends on !throttled (for the case of a large deficit), and if
* we're going inactive then everything else can be deferred
*/
if (cfs_b->idle && !throttled)
goto out_deactivate;
if (!throttled) {
/* mark as potentially idle for the upcoming period */
cfs_b->idle = 1;
return 0;
}
/* account preceding periods in which throttling occurred */
cfs_b->nr_throttled += overrun;
/*
* This check is repeated as we release cfs_b->lock while we unthrottle.
*/
while (throttled && cfs_b->runtime > 0) {
raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
/* we can't nest cfs_b->lock while distributing bandwidth */
throttled = distribute_cfs_runtime(cfs_b);
raw_spin_lock_irqsave(&cfs_b->lock, flags);
}
/*
* While we are ensured activity in the period following an
* unthrottle, this also covers the case in which the new bandwidth is
* insufficient to cover the existing bandwidth deficit. (Forcing the
* timer to remain active while there are any throttled entities.)
*/
cfs_b->idle = 0;
return 0;
out_deactivate:
return 1;
}
/* a cfs_rq won't donate quota below this amount */
static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
/* minimum remaining period time to redistribute slack quota */
static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
/* how long we wait to gather additional slack before distributing */
static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
/*
* Are we near the end of the current quota period?
*
* Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
* hrtimer base being cleared by hrtimer_start. In the case of
* migrate_hrtimers, base is never cleared, so we are fine.
*/
static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
{
struct hrtimer *refresh_timer = &cfs_b->period_timer;
s64 remaining;
/* if the call-back is running a quota refresh is already occurring */
if (hrtimer_callback_running(refresh_timer))
return 1;
/* is a quota refresh about to occur? */
remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
if (remaining < (s64)min_expire)
return 1;
return 0;
}
static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
{
u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
/* if there's a quota refresh soon don't bother with slack */
if (runtime_refresh_within(cfs_b, min_left))
return;
/* don't push forwards an existing deferred unthrottle */
if (cfs_b->slack_started)
return;
cfs_b->slack_started = true;
hrtimer_start(&cfs_b->slack_timer,
ns_to_ktime(cfs_bandwidth_slack_period),
HRTIMER_MODE_REL);
}
/* we know any runtime found here is valid as update_curr() precedes return */
static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
if (slack_runtime <= 0)
return;
raw_spin_lock(&cfs_b->lock);
if (cfs_b->quota != RUNTIME_INF) {
cfs_b->runtime += slack_runtime;
/* we are under rq->lock, defer unthrottling using a timer */
if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
!list_empty(&cfs_b->throttled_cfs_rq))
start_cfs_slack_bandwidth(cfs_b);
}
raw_spin_unlock(&cfs_b->lock);
/* even if it's not valid for return we don't want to try again */
cfs_rq->runtime_remaining -= slack_runtime;
}
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
if (!cfs_bandwidth_used())
return;
if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
return;
__return_cfs_rq_runtime(cfs_rq);
}
/*
* This is done with a timer (instead of inline with bandwidth return) since
* it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
*/
static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
{
u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
unsigned long flags;
/* confirm we're still not at a refresh boundary */
raw_spin_lock_irqsave(&cfs_b->lock, flags);
cfs_b->slack_started = false;
if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
return;
}
if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
runtime = cfs_b->runtime;
raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
if (!runtime)
return;
distribute_cfs_runtime(cfs_b);
}
/*
* When a group wakes up we want to make sure that its quota is not already
* expired/exceeded, otherwise it may be allowed to steal additional ticks of
* runtime as update_curr() throttling can not trigger until it's on-rq.
*/
static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
{
if (!cfs_bandwidth_used())
return;
/* an active group must be handled by the update_curr()->put() path */
if (!cfs_rq->runtime_enabled || cfs_rq->curr)
return;
/* ensure the group is not already throttled */
if (cfs_rq_throttled(cfs_rq))
return;
/* update runtime allocation */
account_cfs_rq_runtime(cfs_rq, 0);
if (cfs_rq->runtime_remaining <= 0)
throttle_cfs_rq(cfs_rq);
}
static void sync_throttle(struct task_group *tg, int cpu)
{
struct cfs_rq *pcfs_rq, *cfs_rq;
if (!cfs_bandwidth_used())
return;
if (!tg->parent)
return;
cfs_rq = tg->cfs_rq[cpu];
pcfs_rq = tg->parent->cfs_rq[cpu];
cfs_rq->throttle_count = pcfs_rq->throttle_count;
cfs_rq->throttled_clock_pelt = rq_clock_pelt(cpu_rq(cpu));
}
/* conditionally throttle active cfs_rq's from put_prev_entity() */
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
if (!cfs_bandwidth_used())
return false;
if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
return false;
/*
* it's possible for a throttled entity to be forced into a running
* state (e.g. set_curr_task), in this case we're finished.
*/
if (cfs_rq_throttled(cfs_rq))
return true;
return throttle_cfs_rq(cfs_rq);
}
static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
{
struct cfs_bandwidth *cfs_b =
container_of(timer, struct cfs_bandwidth, slack_timer);
do_sched_cfs_slack_timer(cfs_b);
return HRTIMER_NORESTART;
}
extern const u64 max_cfs_quota_period;
static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
{
struct cfs_bandwidth *cfs_b =
container_of(timer, struct cfs_bandwidth, period_timer);
unsigned long flags;
int overrun;
int idle = 0;
int count = 0;
raw_spin_lock_irqsave(&cfs_b->lock, flags);
for (;;) {
overrun = hrtimer_forward_now(timer, cfs_b->period);
if (!overrun)
break;
idle = do_sched_cfs_period_timer(cfs_b, overrun, flags);
if (++count > 3) {
u64 new, old = ktime_to_ns(cfs_b->period);
/*
* Grow period by a factor of 2 to avoid losing precision.
* Precision loss in the quota/period ratio can cause __cfs_schedulable
* to fail.
*/
new = old * 2;
if (new < max_cfs_quota_period) {
cfs_b->period = ns_to_ktime(new);
cfs_b->quota *= 2;
cfs_b->burst *= 2;
pr_warn_ratelimited(
"cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us = %lld, cfs_quota_us = %lld)\n",
smp_processor_id(),
div_u64(new, NSEC_PER_USEC),
div_u64(cfs_b->quota, NSEC_PER_USEC));
} else {
pr_warn_ratelimited(
"cfs_period_timer[cpu%d]: period too short, but cannot scale up without losing precision (cfs_period_us = %lld, cfs_quota_us = %lld)\n",
smp_processor_id(),
div_u64(old, NSEC_PER_USEC),
div_u64(cfs_b->quota, NSEC_PER_USEC));
}
/* reset count so we don't come right back in here */
count = 0;
}
}
if (idle)
cfs_b->period_active = 0;
raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
}
void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
raw_spin_lock_init(&cfs_b->lock);
cfs_b->runtime = 0;
cfs_b->quota = RUNTIME_INF;
cfs_b->period = ns_to_ktime(default_cfs_period());
cfs_b->burst = 0;
INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
cfs_b->period_timer.function = sched_cfs_period_timer;
/* Add a random offset so that timers interleave */
hrtimer_set_expires(&cfs_b->period_timer,
get_random_u32_below(cfs_b->period));
hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
cfs_b->slack_timer.function = sched_cfs_slack_timer;
cfs_b->slack_started = false;
}
static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
cfs_rq->runtime_enabled = 0;
INIT_LIST_HEAD(&cfs_rq->throttled_list);
#ifdef CONFIG_SMP
INIT_LIST_HEAD(&cfs_rq->throttled_csd_list);
#endif
}
void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
lockdep_assert_held(&cfs_b->lock);
if (cfs_b->period_active)
return;
cfs_b->period_active = 1;
hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
}
static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
int __maybe_unused i;
/* init_cfs_bandwidth() was not called */
if (!cfs_b->throttled_cfs_rq.next)
return;
hrtimer_cancel(&cfs_b->period_timer);
hrtimer_cancel(&cfs_b->slack_timer);
/*
* It is possible that we still have some cfs_rq's pending on a CSD
* list, though this race is very rare. In order for this to occur, we
* must have raced with the last task leaving the group while there
* exist throttled cfs_rq(s), and the period_timer must have queued the
* CSD item but the remote cpu has not yet processed it. To handle this,
* we can simply flush all pending CSD work inline here. We're
* guaranteed at this point that no additional cfs_rq of this group can
* join a CSD list.
*/
#ifdef CONFIG_SMP
for_each_possible_cpu(i) {
struct rq *rq = cpu_rq(i);
unsigned long flags;
if (list_empty(&rq->cfsb_csd_list))
continue;
local_irq_save(flags);
__cfsb_csd_unthrottle(rq);
local_irq_restore(flags);
}
#endif
}
/*
* Both these CPU hotplug callbacks race against unregister_fair_sched_group()
*
* The race is harmless, since modifying bandwidth settings of unhooked group
* bits doesn't do much.
*/
/* cpu online callback */
static void __maybe_unused update_runtime_enabled(struct rq *rq)
{
struct task_group *tg;
lockdep_assert_rq_held(rq);
rcu_read_lock();
list_for_each_entry_rcu(tg, &task_groups, list) {
struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
raw_spin_lock(&cfs_b->lock);
cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
raw_spin_unlock(&cfs_b->lock);
}
rcu_read_unlock();
}
/* cpu offline callback */
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
{
struct task_group *tg;
lockdep_assert_rq_held(rq);
/*
* The rq clock has already been updated in the
* set_rq_offline(), so we should skip updating
* the rq clock again in unthrottle_cfs_rq().
*/
rq_clock_start_loop_update(rq);
rcu_read_lock();
list_for_each_entry_rcu(tg, &task_groups, list) {
struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
if (!cfs_rq->runtime_enabled)
continue;
/*
* clock_task is not advancing so we just need to make sure
* there's some valid quota amount
*/
cfs_rq->runtime_remaining = 1;
/*
* Offline rq is schedulable till CPU is completely disabled
* in take_cpu_down(), so we prevent new cfs throttling here.
*/
cfs_rq->runtime_enabled = 0;
if (cfs_rq_throttled(cfs_rq))
unthrottle_cfs_rq(cfs_rq);
}
rcu_read_unlock();
rq_clock_stop_loop_update(rq);
}
#else /* CONFIG_CFS_BANDWIDTH */
static inline bool cfs_bandwidth_used(void)
{
return false;
}
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
static inline void sync_throttle(struct task_group *tg, int cpu) {}
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
return 0;
}
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
return 0;
}
static inline int throttled_lb_pair(struct task_group *tg,
int src_cpu, int dest_cpu)
{
return 0;
}
void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
#ifdef CONFIG_FAIR_GROUP_SCHED
static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
#endif
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
return NULL;
}
static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
static inline void update_runtime_enabled(struct rq *rq) {}
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
#endif /* CONFIG_CFS_BANDWIDTH */
/**************************************************
* CFS operations on tasks:
*/
#ifdef CONFIG_SCHED_HRTICK
static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
struct sched_entity *se = &p->se;
struct cfs_rq *cfs_rq = cfs_rq_of(se);
SCHED_WARN_ON(task_rq(p) != rq);
if (rq->cfs.h_nr_running > 1) {
u64 slice = sched_slice(cfs_rq, se);
u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
s64 delta = slice - ran;
if (delta < 0) {
if (task_current(rq, p))
resched_curr(rq);
return;
}
hrtick_start(rq, delta);
}
}
/*
* called from enqueue/dequeue and updates the hrtick when the
* current task is from our class and nr_running is low enough
* to matter.
*/
static void hrtick_update(struct rq *rq)
{
struct task_struct *curr = rq->curr;
if (!hrtick_enabled_fair(rq) || curr->sched_class != &fair_sched_class)
return;
if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
hrtick_start_fair(rq, curr);
}
#else /* !CONFIG_SCHED_HRTICK */
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
static inline void hrtick_update(struct rq *rq)
{
}
#endif
#ifdef CONFIG_SMP
static inline bool cpu_overutilized(int cpu)
{
unsigned long rq_util_min = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MIN);
unsigned long rq_util_max = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MAX);
/* Return true only if the utilization doesn't fit CPU's capacity */
return !util_fits_cpu(cpu_util_cfs(cpu), rq_util_min, rq_util_max, cpu);
}
static inline void update_overutilized_status(struct rq *rq)
{
if (!READ_ONCE(rq->rd->overutilized) && cpu_overutilized(rq->cpu)) {
WRITE_ONCE(rq->rd->overutilized, SG_OVERUTILIZED);
trace_sched_overutilized_tp(rq->rd, SG_OVERUTILIZED);
}
}
#else
static inline void update_overutilized_status(struct rq *rq) { }
#endif
/* Runqueue only has SCHED_IDLE tasks enqueued */
static int sched_idle_rq(struct rq *rq)
{
return unlikely(rq->nr_running == rq->cfs.idle_h_nr_running &&
rq->nr_running);
}
/*
* Returns true if cfs_rq only has SCHED_IDLE entities enqueued. Note the use
* of idle_nr_running, which does not consider idle descendants of normal
* entities.
*/
static bool sched_idle_cfs_rq(struct cfs_rq *cfs_rq)
{
return cfs_rq->nr_running &&
cfs_rq->nr_running == cfs_rq->idle_nr_running;
}
#ifdef CONFIG_SMP
static int sched_idle_cpu(int cpu)
{
return sched_idle_rq(cpu_rq(cpu));
}
#endif
/*
* The enqueue_task method is called before nr_running is
* increased. Here we update the fair scheduling stats and
* then put the task into the rbtree:
*/
static void
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
{
struct cfs_rq *cfs_rq;
struct sched_entity *se = &p->se;
int idle_h_nr_running = task_has_idle_policy(p);
int task_new = !(flags & ENQUEUE_WAKEUP);
/*
* The code below (indirectly) updates schedutil which looks at
* the cfs_rq utilization to select a frequency.
* Let's add the task's estimated utilization to the cfs_rq's
* estimated utilization, before we update schedutil.
*/
util_est_enqueue(&rq->cfs, p);
/*
* If in_iowait is set, the code below may not trigger any cpufreq
* utilization updates, so do it here explicitly with the IOWAIT flag
* passed.
*/
if (p->in_iowait)
cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
for_each_sched_entity(se) {
if (se->on_rq)
break;
cfs_rq = cfs_rq_of(se);
enqueue_entity(cfs_rq, se, flags);
cfs_rq->h_nr_running++;
cfs_rq->idle_h_nr_running += idle_h_nr_running;
if (cfs_rq_is_idle(cfs_rq))
idle_h_nr_running = 1;
/* end evaluation on encountering a throttled cfs_rq */
if (cfs_rq_throttled(cfs_rq))
goto enqueue_throttle;
flags = ENQUEUE_WAKEUP;
}
for_each_sched_entity(se) {
cfs_rq = cfs_rq_of(se);
update_load_avg(cfs_rq, se, UPDATE_TG);
se_update_runnable(se);
update_cfs_group(se);
cfs_rq->h_nr_running++;
cfs_rq->idle_h_nr_running += idle_h_nr_running;
if (cfs_rq_is_idle(cfs_rq))
idle_h_nr_running = 1;
/* end evaluation on encountering a throttled cfs_rq */
if (cfs_rq_throttled(cfs_rq))
goto enqueue_throttle;
}
/* At this point se is NULL and we are at root level*/
add_nr_running(rq, 1);
/*
* Since new tasks are assigned an initial util_avg equal to
* half of the spare capacity of their CPU, tiny tasks have the
* ability to cross the overutilized threshold, which will
* result in the load balancer ruining all the task placement
* done by EAS. As a way to mitigate that effect, do not account
* for the first enqueue operation of new tasks during the
* overutilized flag detection.
*
* A better way of solving this problem would be to wait for
* the PELT signals of tasks to converge before taking them
* into account, but that is not straightforward to implement,
* and the following generally works well enough in practice.
*/
if (!task_new)
update_overutilized_status(rq);
enqueue_throttle:
assert_list_leaf_cfs_rq(rq);
hrtick_update(rq);
}
static void set_next_buddy(struct sched_entity *se);
/*
* The dequeue_task method is called before nr_running is
* decreased. We remove the task from the rbtree and
* update the fair scheduling stats:
*/
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
{
struct cfs_rq *cfs_rq;
struct sched_entity *se = &p->se;
int task_sleep = flags & DEQUEUE_SLEEP;
int idle_h_nr_running = task_has_idle_policy(p);
bool was_sched_idle = sched_idle_rq(rq);
util_est_dequeue(&rq->cfs, p);
for_each_sched_entity(se) {
cfs_rq = cfs_rq_of(se);
dequeue_entity(cfs_rq, se, flags);
cfs_rq->h_nr_running--;
cfs_rq->idle_h_nr_running -= idle_h_nr_running;
if (cfs_rq_is_idle(cfs_rq))
idle_h_nr_running = 1;
/* end evaluation on encountering a throttled cfs_rq */
if (cfs_rq_throttled(cfs_rq))
goto dequeue_throttle;
/* Don't dequeue parent if it has other entities besides us */
if (cfs_rq->load.weight) {
/* Avoid re-evaluating load for this entity: */
se = parent_entity(se);
/*
* Bias pick_next to pick a task from this cfs_rq, as
* p is sleeping when it is within its sched_slice.
*/
if (task_sleep && se && !throttled_hierarchy(cfs_rq))
set_next_buddy(se);
break;
}
flags |= DEQUEUE_SLEEP;
}
for_each_sched_entity(se) {
cfs_rq = cfs_rq_of(se);
update_load_avg(cfs_rq, se, UPDATE_TG);
se_update_runnable(se);
update_cfs_group(se);
cfs_rq->h_nr_running--;
cfs_rq->idle_h_nr_running -= idle_h_nr_running;
if (cfs_rq_is_idle(cfs_rq))
idle_h_nr_running = 1;
/* end evaluation on encountering a throttled cfs_rq */
if (cfs_rq_throttled(cfs_rq))
goto dequeue_throttle;
}
/* At this point se is NULL and we are at root level*/
sub_nr_running(rq, 1);
/* balance early to pull high priority tasks */
if (unlikely(!was_sched_idle && sched_idle_rq(rq)))
rq->next_balance = jiffies;
dequeue_throttle:
util_est_update(&rq->cfs, p, task_sleep);
hrtick_update(rq);
}
#ifdef CONFIG_SMP
/* Working cpumask for: load_balance, load_balance_newidle. */
static DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
static DEFINE_PER_CPU(cpumask_var_t, select_rq_mask);
#ifdef CONFIG_NO_HZ_COMMON
static struct {
cpumask_var_t idle_cpus_mask;
atomic_t nr_cpus;
int has_blocked; /* Idle CPUS has blocked load */
int needs_update; /* Newly idle CPUs need their next_balance collated */
unsigned long next_balance; /* in jiffy units */
unsigned long next_blocked; /* Next update of blocked load in jiffies */
} nohz ____cacheline_aligned;
#endif /* CONFIG_NO_HZ_COMMON */
static unsigned long cpu_load(struct rq *rq)
{
return cfs_rq_load_avg(&rq->cfs);
}
/*
* cpu_load_without - compute CPU load without any contributions from *p
* @cpu: the CPU which load is requested
* @p: the task which load should be discounted
*
* The load of a CPU is defined by the load of tasks currently enqueued on that
* CPU as well as tasks which are currently sleeping after an execution on that
* CPU.
*
* This method returns the load of the specified CPU by discounting the load of
* the specified task, whenever the task is currently contributing to the CPU
* load.
*/
static unsigned long cpu_load_without(struct rq *rq, struct task_struct *p)
{
struct cfs_rq *cfs_rq;
unsigned int load;
/* Task has no contribution or is new */
if (cpu_of(rq) != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
return cpu_load(rq);
cfs_rq = &rq->cfs;
load = READ_ONCE(cfs_rq->avg.load_avg);
/* Discount task's util from CPU's util */
lsub_positive(&load, task_h_load(p));
return load;
}
static unsigned long cpu_runnable(struct rq *rq)
{
return cfs_rq_runnable_avg(&rq->cfs);
}
static unsigned long cpu_runnable_without(struct rq *rq, struct task_struct *p)
{
struct cfs_rq *cfs_rq;
unsigned int runnable;
/* Task has no contribution or is new */
if (cpu_of(rq) != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
return cpu_runnable(rq);
cfs_rq = &rq->cfs;
runnable = READ_ONCE(cfs_rq->avg.runnable_avg);
/* Discount task's runnable from CPU's runnable */
lsub_positive(&runnable, p->se.avg.runnable_avg);
return runnable;
}
static unsigned long capacity_of(int cpu)
{
return cpu_rq(cpu)->cpu_capacity;
}
static void record_wakee(struct task_struct *p)
{
/*
* Only decay a single time; tasks that have less then 1 wakeup per
* jiffy will not have built up many flips.
*/
if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
current->wakee_flips >>= 1;
current->wakee_flip_decay_ts = jiffies;
}
if (current->last_wakee != p) {
current->last_wakee = p;
current->wakee_flips++;
}
}
/*
* Detect M:N waker/wakee relationships via a switching-frequency heuristic.
*
* A waker of many should wake a different task than the one last awakened
* at a frequency roughly N times higher than one of its wakees.
*
* In order to determine whether we should let the load spread vs consolidating
* to shared cache, we look for a minimum 'flip' frequency of llc_size in one
* partner, and a factor of lls_size higher frequency in the other.
*
* With both conditions met, we can be relatively sure that the relationship is
* non-monogamous, with partner count exceeding socket size.
*
* Waker/wakee being client/server, worker/dispatcher, interrupt source or
* whatever is irrelevant, spread criteria is apparent partner count exceeds
* socket size.
*/
static int wake_wide(struct task_struct *p)
{
unsigned int master = current->wakee_flips;
unsigned int slave = p->wakee_flips;
int factor = __this_cpu_read(sd_llc_size);
if (master < slave)
swap(master, slave);
if (slave < factor || master < slave * factor)
return 0;
return 1;
}
/*
* The purpose of wake_affine() is to quickly determine on which CPU we can run
* soonest. For the purpose of speed we only consider the waking and previous
* CPU.
*
* wake_affine_idle() - only considers 'now', it check if the waking CPU is
* cache-affine and is (or will be) idle.
*
* wake_affine_weight() - considers the weight to reflect the average
* scheduling latency of the CPUs. This seems to work
* for the overloaded case.
*/
static int
wake_affine_idle(int this_cpu, int prev_cpu, int sync)
{
/*
* If this_cpu is idle, it implies the wakeup is from interrupt
* context. Only allow the move if cache is shared. Otherwise an
* interrupt intensive workload could force all tasks onto one
* node depending on the IO topology or IRQ affinity settings.
*
* If the prev_cpu is idle and cache affine then avoid a migration.
* There is no guarantee that the cache hot data from an interrupt
* is more important than cache hot data on the prev_cpu and from
* a cpufreq perspective, it's better to have higher utilisation
* on one CPU.
*/
if (available_idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
return available_idle_cpu(prev_cpu) ? prev_cpu : this_cpu;
if (sync && cpu_rq(this_cpu)->nr_running == 1)
return this_cpu;
if (available_idle_cpu(prev_cpu))
return prev_cpu;
return nr_cpumask_bits;
}
static int
wake_affine_weight(struct sched_domain *sd, struct task_struct *p,
int this_cpu, int prev_cpu, int sync)
{
s64 this_eff_load, prev_eff_load;
unsigned long task_load;
this_eff_load = cpu_load(cpu_rq(this_cpu));
if (sync) {
unsigned long current_load = task_h_load(current);
if (current_load > this_eff_load)
return this_cpu;
this_eff_load -= current_load;
}
task_load = task_h_load(p);
this_eff_load += task_load;
if (sched_feat(WA_BIAS))
this_eff_load *= 100;
this_eff_load *= capacity_of(prev_cpu);
prev_eff_load = cpu_load(cpu_rq(prev_cpu));
prev_eff_load -= task_load;
if (sched_feat(WA_BIAS))
prev_eff_load *= 100 + (sd->imbalance_pct - 100) / 2;
prev_eff_load *= capacity_of(this_cpu);
/*
* If sync, adjust the weight of prev_eff_load such that if
* prev_eff == this_eff that select_idle_sibling() will consider
* stacking the wakee on top of the waker if no other CPU is
* idle.
*/
if (sync)
prev_eff_load += 1;
return this_eff_load < prev_eff_load ? this_cpu : nr_cpumask_bits;
}
static int wake_affine(struct sched_domain *sd, struct task_struct *p,
int this_cpu, int prev_cpu, int sync)
{
int target = nr_cpumask_bits;
if (sched_feat(WA_IDLE))
target = wake_affine_idle(this_cpu, prev_cpu, sync);
if (sched_feat(WA_WEIGHT) && target == nr_cpumask_bits)
target = wake_affine_weight(sd, p, this_cpu, prev_cpu, sync);
schedstat_inc(p->stats.nr_wakeups_affine_attempts);
if (target != this_cpu)
return prev_cpu;
schedstat_inc(sd->ttwu_move_affine);
schedstat_inc(p->stats.nr_wakeups_affine);
return target;
}
static struct sched_group *
find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu);
/*
* find_idlest_group_cpu - find the idlest CPU among the CPUs in the group.
*/
static int
find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
{
unsigned long load, min_load = ULONG_MAX;
unsigned int min_exit_latency = UINT_MAX;
u64 latest_idle_timestamp = 0;
int least_loaded_cpu = this_cpu;
int shallowest_idle_cpu = -1;
int i;
/* Check if we have any choice: */
if (group->group_weight == 1)
return cpumask_first(sched_group_span(group));
/* Traverse only the allowed CPUs */
for_each_cpu_and(i, sched_group_span(group), p->cpus_ptr) {
struct rq *rq = cpu_rq(i);
if (!sched_core_cookie_match(rq, p))
continue;
if (sched_idle_cpu(i))
return i;
if (available_idle_cpu(i)) {
struct cpuidle_state *idle = idle_get_state(rq);
if (idle && idle->exit_latency < min_exit_latency) {
/*
* We give priority to a CPU whose idle state
* has the smallest exit latency irrespective
* of any idle timestamp.
*/
min_exit_latency = idle->exit_latency;
latest_idle_timestamp = rq->idle_stamp;
shallowest_idle_cpu = i;
} else if ((!idle || idle->exit_latency == min_exit_latency) &&
rq->idle_stamp > latest_idle_timestamp) {
/*
* If equal or no active idle state, then
* the most recently idled CPU might have
* a warmer cache.
*/
latest_idle_timestamp = rq->idle_stamp;
shallowest_idle_cpu = i;
}
} else if (shallowest_idle_cpu == -1) {
load = cpu_load(cpu_rq(i));
if (load < min_load) {
min_load = load;
least_loaded_cpu = i;
}
}
}
return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
}
static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p,
int cpu, int prev_cpu, int sd_flag)
{
int new_cpu = cpu;
if (!cpumask_intersects(sched_domain_span(sd), p->cpus_ptr))
return prev_cpu;
/*
* We need task's util for cpu_util_without, sync it up to
* prev_cpu's last_update_time.
*/
if (!(sd_flag & SD_BALANCE_FORK))
sync_entity_load_avg(&p->se);
while (sd) {
struct sched_group *group;
struct sched_domain *tmp;
int weight;
if (!(sd->flags & sd_flag)) {
sd = sd->child;
continue;
}
group = find_idlest_group(sd, p, cpu);
if (!group) {
sd = sd->child;
continue;
}
new_cpu = find_idlest_group_cpu(group, p, cpu);
if (new_cpu == cpu) {
/* Now try balancing at a lower domain level of 'cpu': */
sd = sd->child;
continue;
}
/* Now try balancing at a lower domain level of 'new_cpu': */
cpu = new_cpu;
weight = sd->span_weight;
sd = NULL;
for_each_domain(cpu, tmp) {
if (weight <= tmp->span_weight)
break;
if (tmp->flags & sd_flag)
sd = tmp;
}
}
return new_cpu;
}
static inline int __select_idle_cpu(int cpu, struct task_struct *p)
{
if ((available_idle_cpu(cpu) || sched_idle_cpu(cpu)) &&
sched_cpu_cookie_match(cpu_rq(cpu), p))
return cpu;
return -1;
}
#ifdef CONFIG_SCHED_SMT
DEFINE_STATIC_KEY_FALSE(sched_smt_present);
EXPORT_SYMBOL_GPL(sched_smt_present);
static inline void set_idle_cores(int cpu, int val)
{
struct sched_domain_shared *sds;
sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
if (sds)
WRITE_ONCE(sds->has_idle_cores, val);
}
static inline bool test_idle_cores(int cpu)
{
struct sched_domain_shared *sds;
sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
if (sds)
return READ_ONCE(sds->has_idle_cores);
return false;
}
/*
* Scans the local SMT mask to see if the entire core is idle, and records this
* information in sd_llc_shared->has_idle_cores.
*
* Since SMT siblings share all cache levels, inspecting this limited remote
* state should be fairly cheap.
*/
void __update_idle_core(struct rq *rq)
{
int core = cpu_of(rq);
int cpu;
rcu_read_lock();
if (test_idle_cores(core))
goto unlock;
for_each_cpu(cpu, cpu_smt_mask(core)) {
if (cpu == core)
continue;
if (!available_idle_cpu(cpu))
goto unlock;
}
set_idle_cores(core, 1);
unlock:
rcu_read_unlock();
}
/*
* Scan the entire LLC domain for idle cores; this dynamically switches off if
* there are no idle cores left in the system; tracked through
* sd_llc->shared->has_idle_cores and enabled through update_idle_core() above.
*/
static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpus, int *idle_cpu)
{
bool idle = true;
int cpu;
for_each_cpu(cpu, cpu_smt_mask(core)) {
if (!available_idle_cpu(cpu)) {
idle = false;
if (*idle_cpu == -1) {
if (sched_idle_cpu(cpu) && cpumask_test_cpu(cpu, p->cpus_ptr)) {
*idle_cpu = cpu;
break;
}
continue;
}
break;
}
if (*idle_cpu == -1 && cpumask_test_cpu(cpu, p->cpus_ptr))
*idle_cpu = cpu;
}
if (idle)
return core;
cpumask_andnot(cpus, cpus, cpu_smt_mask(core));
return -1;
}
/*
* Scan the local SMT mask for idle CPUs.
*/
static int select_idle_smt(struct task_struct *p, int target)
{
int cpu;
for_each_cpu_and(cpu, cpu_smt_mask(target), p->cpus_ptr) {
if (cpu == target)
continue;
if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
return cpu;
}
return -1;
}
#else /* CONFIG_SCHED_SMT */
static inline void set_idle_cores(int cpu, int val)
{
}
static inline bool test_idle_cores(int cpu)
{
return false;
}
static inline int select_idle_core(struct task_struct *p, int core, struct cpumask *cpus, int *idle_cpu)
{
return __select_idle_cpu(core, p);
}
static inline int select_idle_smt(struct task_struct *p, int target)
{
return -1;
}
#endif /* CONFIG_SCHED_SMT */
/*
* Scan the LLC domain for idle CPUs; this is dynamically regulated by
* comparing the average scan cost (tracked in sd->avg_scan_cost) against the
* average idle time for this rq (as found in rq->avg_idle).
*/
static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool has_idle_core, int target)
{
struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_rq_mask);
int i, cpu, idle_cpu = -1, nr = INT_MAX;
struct sched_domain_shared *sd_share;
struct rq *this_rq = this_rq();
int this = smp_processor_id();
struct sched_domain *this_sd = NULL;
u64 time = 0;
cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
if (sched_feat(SIS_PROP) && !has_idle_core) {
u64 avg_cost, avg_idle, span_avg;
unsigned long now = jiffies;
this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
if (!this_sd)
return -1;
/*
* If we're busy, the assumption that the last idle period
* predicts the future is flawed; age away the remaining
* predicted idle time.
*/
if (unlikely(this_rq->wake_stamp < now)) {
while (this_rq->wake_stamp < now && this_rq->wake_avg_idle) {
this_rq->wake_stamp++;
this_rq->wake_avg_idle >>= 1;
}
}
avg_idle = this_rq->wake_avg_idle;
avg_cost = this_sd->avg_scan_cost + 1;
span_avg = sd->span_weight * avg_idle;
if (span_avg > 4*avg_cost)
nr = div_u64(span_avg, avg_cost);
else
nr = 4;
time = cpu_clock(this);
}
if (sched_feat(SIS_UTIL)) {
sd_share = rcu_dereference(per_cpu(sd_llc_shared, target));
if (sd_share) {
/* because !--nr is the condition to stop scan */
nr = READ_ONCE(sd_share->nr_idle_scan) + 1;
/* overloaded LLC is unlikely to have idle cpu/core */
if (nr == 1)
return -1;
}
}
for_each_cpu_wrap(cpu, cpus, target + 1) {
if (has_idle_core) {
i = select_idle_core(p, cpu, cpus, &idle_cpu);
if ((unsigned int)i < nr_cpumask_bits)
return i;
} else {
if (!--nr)
return -1;
idle_cpu = __select_idle_cpu(cpu, p);
if ((unsigned int)idle_cpu < nr_cpumask_bits)
break;
}
}
if (has_idle_core)
set_idle_cores(target, false);
if (sched_feat(SIS_PROP) && this_sd && !has_idle_core) {
time = cpu_clock(this) - time;
/*
* Account for the scan cost of wakeups against the average
* idle time.
*/
this_rq->wake_avg_idle -= min(this_rq->wake_avg_idle, time);
update_avg(&this_sd->avg_scan_cost, time);
}
return idle_cpu;
}
/*
* For the multiple-LLC per node case, make sure to try the other LLC's if the
* local LLC comes up empty.
*/
static int
select_idle_node(struct task_struct *p, struct sched_domain *sd, int target)
{
struct sched_domain *parent = sd->parent;
struct sched_group *sg;
/* Make sure to not cross nodes. */
if (!parent || parent->flags & SD_NUMA)
return -1;
sg = parent->groups;
do {
int cpu = cpumask_first(sched_group_span(sg));
if (!cpus_share_cache(cpu, target)) {
int i = select_idle_cpu(p, per_cpu(sd_llc, cpu),
test_idle_cores(cpu), cpu);
if ((unsigned)i < nr_cpumask_bits)
return i;
}
sg = sg->next;
} while (sg != parent->groups);
return -1;
}
/*
* Scan the asym_capacity domain for idle CPUs; pick the first idle one on which
* the task fits. If no CPU is big enough, but there are idle ones, try to
* maximize capacity.
*/
static int
select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target)
{
unsigned long task_util, util_min, util_max, best_cap = 0;
int fits, best_fits = 0;
int cpu, best_cpu = -1;
struct cpumask *cpus;
cpus = this_cpu_cpumask_var_ptr(select_rq_mask);
cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
task_util = task_util_est(p);
util_min = uclamp_eff_value(p, UCLAMP_MIN);
util_max = uclamp_eff_value(p, UCLAMP_MAX);
for_each_cpu_wrap(cpu, cpus, target + 1) {
unsigned long cpu_cap = capacity_of(cpu);
if (!available_idle_cpu(cpu) && !sched_idle_cpu(cpu))
continue;
fits = util_fits_cpu(task_util, util_min, util_max, cpu);
/* This CPU fits with all requirements */
if (fits > 0)
return cpu;
/*
* Only the min performance hint (i.e. uclamp_min) doesn't fit.
* Look for the CPU with best capacity.
*/
else if (fits < 0)
cpu_cap = capacity_orig_of(cpu) - thermal_load_avg(cpu_rq(cpu));
/*
* First, select CPU which fits better (-1 being better than 0).
* Then, select the one with best capacity at same level.
*/
if ((fits < best_fits) ||
((fits == best_fits) && (cpu_cap > best_cap))) {
best_cap = cpu_cap;
best_cpu = cpu;
best_fits = fits;
}
}
return best_cpu;
}
static inline bool asym_fits_cpu(unsigned long util,
unsigned long util_min,
unsigned long util_max,
int cpu)
{
if (sched_asym_cpucap_active())
/*
* Return true only if the cpu fully fits the task requirements
* which include the utilization and the performance hints.
*/
return (util_fits_cpu(util, util_min, util_max, cpu) > 0);
return true;
}
/*
* Try and locate an idle core/thread in the LLC cache domain.
*/
static int select_idle_sibling(struct task_struct *p, int prev, int target)
{
bool has_idle_core = false;
struct sched_domain *sd;
unsigned long task_util, util_min, util_max;
int i, recent_used_cpu;
/*
* On asymmetric system, update task utilization because we will check
* that the task fits with cpu's capacity.
*/
if (sched_asym_cpucap_active()) {
sync_entity_load_avg(&p->se);
task_util = task_util_est(p);
util_min = uclamp_eff_value(p, UCLAMP_MIN);
util_max = uclamp_eff_value(p, UCLAMP_MAX);
}
/*
* per-cpu select_rq_mask usage
*/
lockdep_assert_irqs_disabled();
if ((available_idle_cpu(target) || sched_idle_cpu(target)) &&
asym_fits_cpu(task_util, util_min, util_max, target))
return target;
/*
* If the previous CPU is cache affine and idle, don't be stupid:
*/
if (prev != target && cpus_share_cache(prev, target) &&
(available_idle_cpu(prev) || sched_idle_cpu(prev)) &&
asym_fits_cpu(task_util, util_min, util_max, prev))
return prev;
/*
* Allow a per-cpu kthread to stack with the wakee if the
* kworker thread and the tasks previous CPUs are the same.
* The assumption is that the wakee queued work for the
* per-cpu kthread that is now complete and the wakeup is
* essentially a sync wakeup. An obvious example of this
* pattern is IO completions.
*/
if (is_per_cpu_kthread(current) &&
in_task() &&
prev == smp_processor_id() &&
this_rq()->nr_running <= 1 &&
asym_fits_cpu(task_util, util_min, util_max, prev)) {
return prev;
}
/* Check a recently used CPU as a potential idle candidate: */
recent_used_cpu = p->recent_used_cpu;
p->recent_used_cpu = prev;
if (recent_used_cpu != prev &&
recent_used_cpu != target &&
cpus_share_cache(recent_used_cpu, target) &&
(available_idle_cpu(recent_used_cpu) || sched_idle_cpu(recent_used_cpu)) &&
cpumask_test_cpu(recent_used_cpu, p->cpus_ptr) &&
asym_fits_cpu(task_util, util_min, util_max, recent_used_cpu)) {
return recent_used_cpu;
}
/*
* For asymmetric CPU capacity systems, our domain of interest is
* sd_asym_cpucapacity rather than sd_llc.
*/
if (sched_asym_cpucap_active()) {
sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, target));
/*
* On an asymmetric CPU capacity system where an exclusive
* cpuset defines a symmetric island (i.e. one unique
* capacity_orig value through the cpuset), the key will be set
* but the CPUs within that cpuset will not have a domain with
* SD_ASYM_CPUCAPACITY. These should follow the usual symmetric
* capacity path.
*/
if (sd) {
i = select_idle_capacity(p, sd, target);
return ((unsigned)i < nr_cpumask_bits) ? i : target;
}
}
sd = rcu_dereference(per_cpu(sd_llc, target));
if (!sd)
return target;
if (sched_smt_active()) {
has_idle_core = test_idle_cores(target);
if (!has_idle_core && cpus_share_cache(prev, target)) {
i = select_idle_smt(p, prev);
if ((unsigned int)i < nr_cpumask_bits)
return i;
}
}
i = select_idle_cpu(p, sd, has_idle_core, target);
if ((unsigned)i < nr_cpumask_bits)
return i;
if (sched_feat(SIS_NODE)) {
i = select_idle_node(p, sd, target);
if ((unsigned)i < nr_cpumask_bits)
return i;
}
return target;
}
/**
* cpu_util() - Estimates the amount of CPU capacity used by CFS tasks.
* @cpu: the CPU to get the utilization for
* @p: task for which the CPU utilization should be predicted or NULL
* @dst_cpu: CPU @p migrates to, -1 if @p moves from @cpu or @p == NULL
* @boost: 1 to enable boosting, otherwise 0
*
* The unit of the return value must be the same as the one of CPU capacity
* so that CPU utilization can be compared with CPU capacity.
*
* CPU utilization is the sum of running time of runnable tasks plus the
* recent utilization of currently non-runnable tasks on that CPU.
* It represents the amount of CPU capacity currently used by CFS tasks in
* the range [0..max CPU capacity] with max CPU capacity being the CPU
* capacity at f_max.
*
* The estimated CPU utilization is defined as the maximum between CPU
* utilization and sum of the estimated utilization of the currently
* runnable tasks on that CPU. It preserves a utilization "snapshot" of
* previously-executed tasks, which helps better deduce how busy a CPU will
* be when a long-sleeping task wakes up. The contribution to CPU utilization
* of such a task would be significantly decayed at this point of time.
*
* Boosted CPU utilization is defined as max(CPU runnable, CPU utilization).
* CPU contention for CFS tasks can be detected by CPU runnable > CPU
* utilization. Boosting is implemented in cpu_util() so that internal
* users (e.g. EAS) can use it next to external users (e.g. schedutil),
* latter via cpu_util_cfs_boost().
*
* CPU utilization can be higher than the current CPU capacity
* (f_curr/f_max * max CPU capacity) or even the max CPU capacity because
* of rounding errors as well as task migrations or wakeups of new tasks.
* CPU utilization has to be capped to fit into the [0..max CPU capacity]
* range. Otherwise a group of CPUs (CPU0 util = 121% + CPU1 util = 80%)
* could be seen as over-utilized even though CPU1 has 20% of spare CPU
* capacity. CPU utilization is allowed to overshoot current CPU capacity
* though since this is useful for predicting the CPU capacity required
* after task migrations (scheduler-driven DVFS).
*
* Return: (Boosted) (estimated) utilization for the specified CPU.
*/
static unsigned long
cpu_util(int cpu, struct task_struct *p, int dst_cpu, int boost)
{
struct cfs_rq *cfs_rq = &cpu_rq(cpu)->cfs;
unsigned long util = READ_ONCE(cfs_rq->avg.util_avg);
unsigned long runnable;
if (boost) {
runnable = READ_ONCE(cfs_rq->avg.runnable_avg);
util = max(util, runnable);
}
/*
* If @dst_cpu is -1 or @p migrates from @cpu to @dst_cpu remove its
* contribution. If @p migrates from another CPU to @cpu add its
* contribution. In all the other cases @cpu is not impacted by the
* migration so its util_avg is already correct.
*/
if (p && task_cpu(p) == cpu && dst_cpu != cpu)
lsub_positive(&util, task_util(p));
else if (p && task_cpu(p) != cpu && dst_cpu == cpu)
util += task_util(p);
if (sched_feat(UTIL_EST)) {
unsigned long util_est;
util_est = READ_ONCE(cfs_rq->avg.util_est.enqueued);
/*
* During wake-up @p isn't enqueued yet and doesn't contribute
* to any cpu_rq(cpu)->cfs.avg.util_est.enqueued.
* If @dst_cpu == @cpu add it to "simulate" cpu_util after @p
* has been enqueued.
*
* During exec (@dst_cpu = -1) @p is enqueued and does
* contribute to cpu_rq(cpu)->cfs.util_est.enqueued.
* Remove it to "simulate" cpu_util without @p's contribution.
*
* Despite the task_on_rq_queued(@p) check there is still a
* small window for a possible race when an exec
* select_task_rq_fair() races with LB's detach_task().
*
* detach_task()
* deactivate_task()
* p->on_rq = TASK_ON_RQ_MIGRATING;
* -------------------------------- A
* dequeue_task() \
* dequeue_task_fair() + Race Time
* util_est_dequeue() /
* -------------------------------- B
*
* The additional check "current == p" is required to further
* reduce the race window.
*/
if (dst_cpu == cpu)
util_est += _task_util_est(p);
else if (p && unlikely(task_on_rq_queued(p) || current == p))
lsub_positive(&util_est, _task_util_est(p));
util = max(util, util_est);
}
return min(util, capacity_orig_of(cpu));
}
unsigned long cpu_util_cfs(int cpu)
{
return cpu_util(cpu, NULL, -1, 0);
}
unsigned long cpu_util_cfs_boost(int cpu)
{
return cpu_util(cpu, NULL, -1, 1);
}
/*
* cpu_util_without: compute cpu utilization without any contributions from *p
* @cpu: the CPU which utilization is requested
* @p: the task which utilization should be discounted
*
* The utilization of a CPU is defined by the utilization of tasks currently
* enqueued on that CPU as well as tasks which are currently sleeping after an
* execution on that CPU.
*
* This method returns the utilization of the specified CPU by discounting the
* utilization of the specified task, whenever the task is currently
* contributing to the CPU utilization.
*/
static unsigned long cpu_util_without(int cpu, struct task_struct *p)
{
/* Task has no contribution or is new */
if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
p = NULL;
return cpu_util(cpu, p, -1, 0);
}
/*
* energy_env - Utilization landscape for energy estimation.
* @task_busy_time: Utilization contribution by the task for which we test the
* placement. Given by eenv_task_busy_time().
* @pd_busy_time: Utilization of the whole perf domain without the task
* contribution. Given by eenv_pd_busy_time().
* @cpu_cap: Maximum CPU capacity for the perf domain.
* @pd_cap: Entire perf domain capacity. (pd->nr_cpus * cpu_cap).
*/
struct energy_env {
unsigned long task_busy_time;
unsigned long pd_busy_time;
unsigned long cpu_cap;
unsigned long pd_cap;
};
/*
* Compute the task busy time for compute_energy(). This time cannot be
* injected directly into effective_cpu_util() because of the IRQ scaling.
* The latter only makes sense with the most recent CPUs where the task has
* run.
*/
static inline void eenv_task_busy_time(struct energy_env *eenv,
struct task_struct *p, int prev_cpu)
{
unsigned long busy_time, max_cap = arch_scale_cpu_capacity(prev_cpu);
unsigned long irq = cpu_util_irq(cpu_rq(prev_cpu));
if (unlikely(irq >= max_cap))
busy_time = max_cap;
else
busy_time = scale_irq_capacity(task_util_est(p), irq, max_cap);
eenv->task_busy_time = busy_time;
}
/*
* Compute the perf_domain (PD) busy time for compute_energy(). Based on the
* utilization for each @pd_cpus, it however doesn't take into account
* clamping since the ratio (utilization / cpu_capacity) is already enough to
* scale the EM reported power consumption at the (eventually clamped)
* cpu_capacity.
*
* The contribution of the task @p for which we want to estimate the
* energy cost is removed (by cpu_util()) and must be calculated
* separately (see eenv_task_busy_time). This ensures:
*
* - A stable PD utilization, no matter which CPU of that PD we want to place
* the task on.
*
* - A fair comparison between CPUs as the task contribution (task_util())
* will always be the same no matter which CPU utilization we rely on
* (util_avg or util_est).
*
* Set @eenv busy time for the PD that spans @pd_cpus. This busy time can't
* exceed @eenv->pd_cap.
*/
static inline void eenv_pd_busy_time(struct energy_env *eenv,
struct cpumask *pd_cpus,
struct task_struct *p)
{
unsigned long busy_time = 0;
int cpu;
for_each_cpu(cpu, pd_cpus) {
unsigned long util = cpu_util(cpu, p, -1, 0);
busy_time += effective_cpu_util(cpu, util, ENERGY_UTIL, NULL);
}
eenv->pd_busy_time = min(eenv->pd_cap, busy_time);
}
/*
* Compute the maximum utilization for compute_energy() when the task @p
* is placed on the cpu @dst_cpu.
*
* Returns the maximum utilization among @eenv->cpus. This utilization can't
* exceed @eenv->cpu_cap.
*/
static inline unsigned long
eenv_pd_max_util(struct energy_env *eenv, struct cpumask *pd_cpus,
struct task_struct *p, int dst_cpu)
{
unsigned long max_util = 0;
int cpu;
for_each_cpu(cpu, pd_cpus) {
struct task_struct *tsk = (cpu == dst_cpu) ? p : NULL;
unsigned long util = cpu_util(cpu, p, dst_cpu, 1);
unsigned long eff_util;
/*
* Performance domain frequency: utilization clamping
* must be considered since it affects the selection
* of the performance domain frequency.
* NOTE: in case RT tasks are running, by default the
* FREQUENCY_UTIL's utilization can be max OPP.
*/
eff_util = effective_cpu_util(cpu, util, FREQUENCY_UTIL, tsk);
max_util = max(max_util, eff_util);
}
return min(max_util, eenv->cpu_cap);
}
/*
* compute_energy(): Use the Energy Model to estimate the energy that @pd would
* consume for a given utilization landscape @eenv. When @dst_cpu < 0, the task
* contribution is ignored.
*/
static inline unsigned long
compute_energy(struct energy_env *eenv, struct perf_domain *pd,
struct cpumask *pd_cpus, struct task_struct *p, int dst_cpu)
{
unsigned long max_util = eenv_pd_max_util(eenv, pd_cpus, p, dst_cpu);
unsigned long busy_time = eenv->pd_busy_time;
if (dst_cpu >= 0)
busy_time = min(eenv->pd_cap, busy_time + eenv->task_busy_time);
return em_cpu_energy(pd->em_pd, max_util, busy_time, eenv->cpu_cap);
}
/*
* find_energy_efficient_cpu(): Find most energy-efficient target CPU for the
* waking task. find_energy_efficient_cpu() looks for the CPU with maximum
* spare capacity in each performance domain and uses it as a potential
* candidate to execute the task. Then, it uses the Energy Model to figure
* out which of the CPU candidates is the most energy-efficient.
*
* The rationale for this heuristic is as follows. In a performance domain,
* all the most energy efficient CPU candidates (according to the Energy
* Model) are those for which we'll request a low frequency. When there are
* several CPUs for which the frequency request will be the same, we don't
* have enough data to break the tie between them, because the Energy Model
* only includes active power costs. With this model, if we assume that
* frequency requests follow utilization (e.g. using schedutil), the CPU with
* the maximum spare capacity in a performance domain is guaranteed to be among
* the best candidates of the performance domain.
*
* In practice, it could be preferable from an energy standpoint to pack
* small tasks on a CPU in order to let other CPUs go in deeper idle states,
* but that could also hurt our chances to go cluster idle, and we have no
* ways to tell with the current Energy Model if this is actually a good
* idea or not. So, find_energy_efficient_cpu() basically favors
* cluster-packing, and spreading inside a cluster. That should at least be
* a good thing for latency, and this is consistent with the idea that most
* of the energy savings of EAS come from the asymmetry of the system, and
* not so much from breaking the tie between identical CPUs. That's also the
* reason why EAS is enabled in the topology code only for systems where
* SD_ASYM_CPUCAPACITY is set.
*
* NOTE: Forkees are not accepted in the energy-aware wake-up path because
* they don't have any useful utilization data yet and it's not possible to
* forecast their impact on energy consumption. Consequently, they will be
* placed by find_idlest_cpu() on the least loaded CPU, which might turn out
* to be energy-inefficient in some use-cases. The alternative would be to
* bias new tasks towards specific types of CPUs first, or to try to infer
* their util_avg from the parent task, but those heuristics could hurt
* other use-cases too. So, until someone finds a better way to solve this,
* let's keep things simple by re-using the existing slow path.
*/
static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
{
struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_rq_mask);
unsigned long prev_delta = ULONG_MAX, best_delta = ULONG_MAX;
unsigned long p_util_min = uclamp_is_used() ? uclamp_eff_value(p, UCLAMP_MIN) : 0;
unsigned long p_util_max = uclamp_is_used() ? uclamp_eff_value(p, UCLAMP_MAX) : 1024;
struct root_domain *rd = this_rq()->rd;
int cpu, best_energy_cpu, target = -1;
int prev_fits = -1, best_fits = -1;
unsigned long best_thermal_cap = 0;
unsigned long prev_thermal_cap = 0;
struct sched_domain *sd;
struct perf_domain *pd;
struct energy_env eenv;
rcu_read_lock();
pd = rcu_dereference(rd->pd);
if (!pd || READ_ONCE(rd->overutilized))
goto unlock;
/*
* Energy-aware wake-up happens on the lowest sched_domain starting
* from sd_asym_cpucapacity spanning over this_cpu and prev_cpu.
*/
sd = rcu_dereference(*this_cpu_ptr(&sd_asym_cpucapacity));
while (sd && !cpumask_test_cpu(prev_cpu, sched_domain_span(sd)))
sd = sd->parent;
if (!sd)
goto unlock;
target = prev_cpu;
sync_entity_load_avg(&p->se);
if (!uclamp_task_util(p, p_util_min, p_util_max))
goto unlock;
eenv_task_busy_time(&eenv, p, prev_cpu);
for (; pd; pd = pd->next) {
unsigned long util_min = p_util_min, util_max = p_util_max;
unsigned long cpu_cap, cpu_thermal_cap, util;
unsigned long cur_delta, max_spare_cap = 0;
unsigned long rq_util_min, rq_util_max;
unsigned long prev_spare_cap = 0;
int max_spare_cap_cpu = -1;
unsigned long base_energy;
int fits, max_fits = -1;
cpumask_and(cpus, perf_domain_span(pd), cpu_online_mask);
if (cpumask_empty(cpus))
continue;
/* Account thermal pressure for the energy estimation */
cpu = cpumask_first(cpus);
cpu_thermal_cap = arch_scale_cpu_capacity(cpu);
cpu_thermal_cap -= arch_scale_thermal_pressure(cpu);
eenv.cpu_cap = cpu_thermal_cap;
eenv.pd_cap = 0;
for_each_cpu(cpu, cpus) {
struct rq *rq = cpu_rq(cpu);
eenv.pd_cap += cpu_thermal_cap;
if (!cpumask_test_cpu(cpu, sched_domain_span(sd)))
continue;
if (!cpumask_test_cpu(cpu, p->cpus_ptr))
continue;
util = cpu_util(cpu, p, cpu, 0);
cpu_cap = capacity_of(cpu);
/*
* Skip CPUs that cannot satisfy the capacity request.
* IOW, placing the task there would make the CPU
* overutilized. Take uclamp into account to see how
* much capacity we can get out of the CPU; this is
* aligned with sched_cpu_util().
*/
if (uclamp_is_used() && !uclamp_rq_is_idle(rq)) {
/*
* Open code uclamp_rq_util_with() except for
* the clamp() part. Ie: apply max aggregation
* only. util_fits_cpu() logic requires to
* operate on non clamped util but must use the
* max-aggregated uclamp_{min, max}.
*/
rq_util_min = uclamp_rq_get(rq, UCLAMP_MIN);
rq_util_max = uclamp_rq_get(rq, UCLAMP_MAX);
util_min = max(rq_util_min, p_util_min);
util_max = max(rq_util_max, p_util_max);
}
fits = util_fits_cpu(util, util_min, util_max, cpu);
if (!fits)
continue;
lsub_positive(&cpu_cap, util);
if (cpu == prev_cpu) {
/* Always use prev_cpu as a candidate. */
prev_spare_cap = cpu_cap;
prev_fits = fits;
} else if ((fits > max_fits) ||
((fits == max_fits) && (cpu_cap > max_spare_cap))) {
/*
* Find the CPU with the maximum spare capacity
* among the remaining CPUs in the performance
* domain.
*/
max_spare_cap = cpu_cap;
max_spare_cap_cpu = cpu;
max_fits = fits;
}
}
if (max_spare_cap_cpu < 0 && prev_spare_cap == 0)
continue;
eenv_pd_busy_time(&eenv, cpus, p);
/* Compute the 'base' energy of the pd, without @p */
base_energy = compute_energy(&eenv, pd, cpus, p, -1);
/* Evaluate the energy impact of using prev_cpu. */
if (prev_spare_cap > 0) {
prev_delta = compute_energy(&eenv, pd, cpus, p,
prev_cpu);
/* CPU utilization has changed */
if (prev_delta < base_energy)
goto unlock;
prev_delta -= base_energy;
prev_thermal_cap = cpu_thermal_cap;
best_delta = min(best_delta, prev_delta);
}
/* Evaluate the energy impact of using max_spare_cap_cpu. */
if (max_spare_cap_cpu >= 0 && max_spare_cap > prev_spare_cap) {
/* Current best energy cpu fits better */
if (max_fits < best_fits)
continue;
/*
* Both don't fit performance hint (i.e. uclamp_min)
* but best energy cpu has better capacity.
*/
if ((max_fits < 0) &&
(cpu_thermal_cap <= best_thermal_cap))
continue;
cur_delta = compute_energy(&eenv, pd, cpus, p,
max_spare_cap_cpu);
/* CPU utilization has changed */
if (cur_delta < base_energy)
goto unlock;
cur_delta -= base_energy;
/*
* Both fit for the task but best energy cpu has lower
* energy impact.
*/
if ((max_fits > 0) && (best_fits > 0) &&
(cur_delta >= best_delta))
continue;
best_delta = cur_delta;
best_energy_cpu = max_spare_cap_cpu;
best_fits = max_fits;
best_thermal_cap = cpu_thermal_cap;
}
}
rcu_read_unlock();
if ((best_fits > prev_fits) ||
((best_fits > 0) && (best_delta < prev_delta)) ||
((best_fits < 0) && (best_thermal_cap > prev_thermal_cap)))
target = best_energy_cpu;
return target;
unlock:
rcu_read_unlock();
return target;
}
/*
* select_task_rq_fair: Select target runqueue for the waking task in domains
* that have the relevant SD flag set. In practice, this is SD_BALANCE_WAKE,
* SD_BALANCE_FORK, or SD_BALANCE_EXEC.
*
* Balances load by selecting the idlest CPU in the idlest group, or under
* certain conditions an idle sibling CPU if the domain has SD_WAKE_AFFINE set.
*
* Returns the target CPU number.
*/
static int
select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
{
int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING);
struct sched_domain *tmp, *sd = NULL;
int cpu = smp_processor_id();
int new_cpu = prev_cpu;
int want_affine = 0;
/* SD_flags and WF_flags share the first nibble */
int sd_flag = wake_flags & 0xF;
/*
* required for stable ->cpus_allowed
*/
lockdep_assert_held(&p->pi_lock);
if (wake_flags & WF_TTWU) {
record_wakee(p);
if (sched_energy_enabled()) {
new_cpu = find_energy_efficient_cpu(p, prev_cpu);
if (new_cpu >= 0)
return new_cpu;
new_cpu = prev_cpu;
}
want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, p->cpus_ptr);
}
rcu_read_lock();
for_each_domain(cpu, tmp) {
/*
* If both 'cpu' and 'prev_cpu' are part of this domain,
* cpu is a valid SD_WAKE_AFFINE target.
*/
if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
if (cpu != prev_cpu)
new_cpu = wake_affine(tmp, p, cpu, prev_cpu, sync);
sd = NULL; /* Prefer wake_affine over balance flags */
break;
}
/*
* Usually only true for WF_EXEC and WF_FORK, as sched_domains
* usually do not have SD_BALANCE_WAKE set. That means wakeup
* will usually go to the fast path.
*/
if (tmp->flags & sd_flag)
sd = tmp;
else if (!want_affine)
break;
}
if (unlikely(sd)) {
/* Slow path */
new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);
} else if (wake_flags & WF_TTWU) { /* XXX always ? */
/* Fast path */
new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
}
rcu_read_unlock();
return new_cpu;
}
/*
* Called immediately before a task is migrated to a new CPU; task_cpu(p) and
* cfs_rq_of(p) references at time of call are still valid and identify the
* previous CPU. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
*/
static void migrate_task_rq_fair(struct task_struct *p, int new_cpu)
{
struct sched_entity *se = &p->se;
/*
* As blocked tasks retain absolute vruntime the migration needs to
* deal with this by subtracting the old and adding the new
* min_vruntime -- the latter is done by enqueue_entity() when placing
* the task on the new runqueue.
*/
if (READ_ONCE(p->__state) == TASK_WAKING) {
struct cfs_rq *cfs_rq = cfs_rq_of(se);
se->vruntime -= u64_u32_load(cfs_rq->min_vruntime);
}
if (!task_on_rq_migrating(p)) {
remove_entity_load_avg(se);
/*
* Here, the task's PELT values have been updated according to
* the current rq's clock. But if that clock hasn't been
* updated in a while, a substantial idle time will be missed,
* leading to an inflation after wake-up on the new rq.
*
* Estimate the missing time from the cfs_rq last_update_time
* and update sched_avg to improve the PELT continuity after
* migration.
*/
migrate_se_pelt_lag(se);
}
/* Tell new CPU we are migrated */
se->avg.last_update_time = 0;
update_scan_period(p, new_cpu);
}
static void task_dead_fair(struct task_struct *p)
{
remove_entity_load_avg(&p->se);
}
static int
balance_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
{
if (rq->nr_running)
return 1;
return newidle_balance(rq, rf) != 0;
}
#endif /* CONFIG_SMP */
static unsigned long wakeup_gran(struct sched_entity *se)
{
unsigned long gran = sysctl_sched_wakeup_granularity;
/*
* Since its curr running now, convert the gran from real-time
* to virtual-time in his units.
*
* By using 'se' instead of 'curr' we penalize light tasks, so
* they get preempted easier. That is, if 'se' < 'curr' then
* the resulting gran will be larger, therefore penalizing the
* lighter, if otoh 'se' > 'curr' then the resulting gran will
* be smaller, again penalizing the lighter task.
*
* This is especially important for buddies when the leftmost
* task is higher priority than the buddy.
*/
return calc_delta_fair(gran, se);
}
/*
* Should 'se' preempt 'curr'.
*
* |s1
* |s2
* |s3
* g
* |<--->|c
*
* w(c, s1) = -1
* w(c, s2) = 0
* w(c, s3) = 1
*
*/
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
{
s64 gran, vdiff = curr->vruntime - se->vruntime;
if (vdiff <= 0)
return -1;
gran = wakeup_gran(se);
if (vdiff > gran)
return 1;
return 0;
}
static void set_last_buddy(struct sched_entity *se)
{
for_each_sched_entity(se) {
if (SCHED_WARN_ON(!se->on_rq))
return;
if (se_is_idle(se))
return;
cfs_rq_of(se)->last = se;
}
}
static void set_next_buddy(struct sched_entity *se)
{
for_each_sched_entity(se) {
if (SCHED_WARN_ON(!se->on_rq))
return;
if (se_is_idle(se))
return;
cfs_rq_of(se)->next = se;
}
}
static void set_skip_buddy(struct sched_entity *se)
{
for_each_sched_entity(se)
cfs_rq_of(se)->skip = se;
}
/*
* Preempt the current task with a newly woken task if needed:
*/
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
{
struct task_struct *curr = rq->curr;
struct sched_entity *se = &curr->se, *pse = &p->se;
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
int scale = cfs_rq->nr_running >= sched_nr_latency;
int next_buddy_marked = 0;
int cse_is_idle, pse_is_idle;
if (unlikely(se == pse))
return;
/*
* This is possible from callers such as attach_tasks(), in which we
* unconditionally check_preempt_curr() after an enqueue (which may have
* lead to a throttle). This both saves work and prevents false
* next-buddy nomination below.
*/
if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
return;
if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
set_next_buddy(pse);
next_buddy_marked = 1;
}
/*
* We can come here with TIF_NEED_RESCHED already set from new task
* wake up path.
*
* Note: this also catches the edge-case of curr being in a throttled
* group (e.g. via set_curr_task), since update_curr() (in the
* enqueue of curr) will have resulted in resched being set. This
* prevents us from potentially nominating it as a false LAST_BUDDY
* below.
*/
if (test_tsk_need_resched(curr))
return;
/* Idle tasks are by definition preempted by non-idle tasks. */
if (unlikely(task_has_idle_policy(curr)) &&
likely(!task_has_idle_policy(p)))
goto preempt;
/*
* Batch and idle tasks do not preempt non-idle tasks (their preemption
* is driven by the tick):
*/
if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
return;
find_matching_se(&se, &pse);
WARN_ON_ONCE(!pse);
cse_is_idle = se_is_idle(se);
pse_is_idle = se_is_idle(pse);
/*
* Preempt an idle group in favor of a non-idle group (and don't preempt
* in the inverse case).
*/
if (cse_is_idle && !pse_is_idle)
goto preempt;
if (cse_is_idle != pse_is_idle)
return;
update_curr(cfs_rq_of(se));
if (wakeup_preempt_entity(se, pse) == 1) {
/*
* Bias pick_next to pick the sched entity that is
* triggering this preemption.
*/
if (!next_buddy_marked)
set_next_buddy(pse);
goto preempt;
}
return;
preempt:
resched_curr(rq);
/*
* Only set the backward buddy when the current task is still
* on the rq. This can happen when a wakeup gets interleaved
* with schedule on the ->pre_schedule() or idle_balance()
* point, either of which can * drop the rq lock.
*
* Also, during early boot the idle thread is in the fair class,
* for obvious reasons its a bad idea to schedule back to it.
*/
if (unlikely(!se->on_rq || curr == rq->idle))
return;
if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
set_last_buddy(se);
}
#ifdef CONFIG_SMP
static struct task_struct *pick_task_fair(struct rq *rq)
{
struct sched_entity *se;
struct cfs_rq *cfs_rq;
again:
cfs_rq = &rq->cfs;
if (!cfs_rq->nr_running)
return NULL;
do {
struct sched_entity *curr = cfs_rq->curr;
/* When we pick for a remote RQ, we'll not have done put_prev_entity() */
if (curr) {
if (curr->on_rq)
update_curr(cfs_rq);
else
curr = NULL;
if (unlikely(check_cfs_rq_runtime(cfs_rq)))
goto again;
}
se = pick_next_entity(cfs_rq, curr);
cfs_rq = group_cfs_rq(se);
} while (cfs_rq);
return task_of(se);
}
#endif
struct task_struct *
pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
{
struct cfs_rq *cfs_rq = &rq->cfs;
struct sched_entity *se;
struct task_struct *p;
int new_tasks;
again:
if (!sched_fair_runnable(rq))
goto idle;
#ifdef CONFIG_FAIR_GROUP_SCHED
if (!prev || prev->sched_class != &fair_sched_class)
goto simple;
/*
* Because of the set_next_buddy() in dequeue_task_fair() it is rather
* likely that a next task is from the same cgroup as the current.
*
* Therefore attempt to avoid putting and setting the entire cgroup
* hierarchy, only change the part that actually changes.
*/
do {
struct sched_entity *curr = cfs_rq->curr;
/*
* Since we got here without doing put_prev_entity() we also
* have to consider cfs_rq->curr. If it is still a runnable
* entity, update_curr() will update its vruntime, otherwise
* forget we've ever seen it.
*/
if (curr) {
if (curr->on_rq)
update_curr(cfs_rq);
else
curr = NULL;
/*
* This call to check_cfs_rq_runtime() will do the
* throttle and dequeue its entity in the parent(s).
* Therefore the nr_running test will indeed
* be correct.
*/
if (unlikely(check_cfs_rq_runtime(cfs_rq))) {
cfs_rq = &rq->cfs;
if (!cfs_rq->nr_running)
goto idle;
goto simple;
}
}
se = pick_next_entity(cfs_rq, curr);
cfs_rq = group_cfs_rq(se);
} while (cfs_rq);
p = task_of(se);
/*
* Since we haven't yet done put_prev_entity and if the selected task
* is a different task than we started out with, try and touch the
* least amount of cfs_rqs.
*/
if (prev != p) {
struct sched_entity *pse = &prev->se;
while (!(cfs_rq = is_same_group(se, pse))) {
int se_depth = se->depth;
int pse_depth = pse->depth;
if (se_depth <= pse_depth) {
put_prev_entity(cfs_rq_of(pse), pse);
pse = parent_entity(pse);
}
if (se_depth >= pse_depth) {
set_next_entity(cfs_rq_of(se), se);
se = parent_entity(se);
}
}
put_prev_entity(cfs_rq, pse);
set_next_entity(cfs_rq, se);
}
goto done;
simple:
#endif
if (prev)
put_prev_task(rq, prev);
do {
se = pick_next_entity(cfs_rq, NULL);
set_next_entity(cfs_rq, se);
cfs_rq = group_cfs_rq(se);
} while (cfs_rq);
p = task_of(se);
done: __maybe_unused;
#ifdef CONFIG_SMP
/*
* Move the next running task to the front of
* the list, so our cfs_tasks list becomes MRU
* one.
*/
list_move(&p->se.group_node, &rq->cfs_tasks);
#endif
if (hrtick_enabled_fair(rq))
hrtick_start_fair(rq, p);
update_misfit_status(p, rq);
return p;
idle:
if (!rf)
return NULL;
new_tasks = newidle_balance(rq, rf);
/*
* Because newidle_balance() releases (and re-acquires) rq->lock, it is
* possible for any higher priority task to appear. In that case we
* must re-start the pick_next_entity() loop.
*/
if (new_tasks < 0)
return RETRY_TASK;
if (new_tasks > 0)
goto again;
/*
* rq is about to be idle, check if we need to update the
* lost_idle_time of clock_pelt
*/
update_idle_rq_clock_pelt(rq);
return NULL;
}
static struct task_struct *__pick_next_task_fair(struct rq *rq)
{
return pick_next_task_fair(rq, NULL, NULL);
}
/*
* Account for a descheduled task:
*/
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
{
struct sched_entity *se = &prev->se;
struct cfs_rq *cfs_rq;
for_each_sched_entity(se) {
cfs_rq = cfs_rq_of(se);
put_prev_entity(cfs_rq, se);
}
}
/*
* sched_yield() is very simple
*
* The magic of dealing with the ->skip buddy is in pick_next_entity.
*/
static void yield_task_fair(struct rq *rq)
{
struct task_struct *curr = rq->curr;
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
struct sched_entity *se = &curr->se;
/*
* Are we the only task in the tree?
*/
if (unlikely(rq->nr_running == 1))
return;
clear_buddies(cfs_rq, se);
if (curr->policy != SCHED_BATCH) {
update_rq_clock(rq);
/*
* Update run-time statistics of the 'current'.
*/
update_curr(cfs_rq);
/*
* Tell update_rq_clock() that we've just updated,
* so we don't do microscopic update in schedule()
* and double the fastpath cost.
*/
rq_clock_skip_update(rq);
}
set_skip_buddy(se);
}
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p)
{
struct sched_entity *se = &p->se;
/* throttled hierarchies are not runnable */
if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
return false;
/* Tell the scheduler that we'd really like pse to run next. */
set_next_buddy(se);
yield_task_fair(rq);
return true;
}
#ifdef CONFIG_SMP
/**************************************************
* Fair scheduling class load-balancing methods.
*
* BASICS
*
* The purpose of load-balancing is to achieve the same basic fairness the
* per-CPU scheduler provides, namely provide a proportional amount of compute
* time to each task. This is expressed in the following equation:
*
* W_i,n/P_i == W_j,n/P_j for all i,j (1)
*
* Where W_i,n is the n-th weight average for CPU i. The instantaneous weight
* W_i,0 is defined as:
*
* W_i,0 = \Sum_j w_i,j (2)
*
* Where w_i,j is the weight of the j-th runnable task on CPU i. This weight
* is derived from the nice value as per sched_prio_to_weight[].
*
* The weight average is an exponential decay average of the instantaneous
* weight:
*
* W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
*
* C_i is the compute capacity of CPU i, typically it is the
* fraction of 'recent' time available for SCHED_OTHER task execution. But it
* can also include other factors [XXX].
*
* To achieve this balance we define a measure of imbalance which follows
* directly from (1):
*
* imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
*
* We them move tasks around to minimize the imbalance. In the continuous
* function space it is obvious this converges, in the discrete case we get
* a few fun cases generally called infeasible weight scenarios.
*
* [XXX expand on:
* - infeasible weights;
* - local vs global optima in the discrete case. ]
*
*
* SCHED DOMAINS
*
* In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
* for all i,j solution, we create a tree of CPUs that follows the hardware
* topology where each level pairs two lower groups (or better). This results
* in O(log n) layers. Furthermore we reduce the number of CPUs going up the
* tree to only the first of the previous level and we decrease the frequency
* of load-balance at each level inv. proportional to the number of CPUs in
* the groups.
*
* This yields:
*
* log_2 n 1 n
* \Sum { --- * --- * 2^i } = O(n) (5)
* i = 0 2^i 2^i
* `- size of each group
* | | `- number of CPUs doing load-balance
* | `- freq
* `- sum over all levels
*
* Coupled with a limit on how many tasks we can migrate every balance pass,
* this makes (5) the runtime complexity of the balancer.
*
* An important property here is that each CPU is still (indirectly) connected
* to every other CPU in at most O(log n) steps:
*
* The adjacency matrix of the resulting graph is given by:
*
* log_2 n
* A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
* k = 0
*
* And you'll find that:
*
* A^(log_2 n)_i,j != 0 for all i,j (7)
*
* Showing there's indeed a path between every CPU in at most O(log n) steps.
* The task movement gives a factor of O(m), giving a convergence complexity
* of:
*
* O(nm log n), n := nr_cpus, m := nr_tasks (8)
*
*
* WORK CONSERVING
*
* In order to avoid CPUs going idle while there's still work to do, new idle
* balancing is more aggressive and has the newly idle CPU iterate up the domain
* tree itself instead of relying on other CPUs to bring it work.
*
* This adds some complexity to both (5) and (8) but it reduces the total idle
* time.
*
* [XXX more?]
*
*
* CGROUPS
*
* Cgroups make a horror show out of (2), instead of a simple sum we get:
*
* s_k,i
* W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
* S_k
*
* Where
*
* s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
*
* w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on CPU i.
*
* The big problem is S_k, its a global sum needed to compute a local (W_i)
* property.
*
* [XXX write more on how we solve this.. _after_ merging pjt's patches that
* rewrite all of this once again.]
*/
static unsigned long __read_mostly max_load_balance_interval = HZ/10;
enum fbq_type { regular, remote, all };
/*
* 'group_type' describes the group of CPUs at the moment of load balancing.
*
* The enum is ordered by pulling priority, with the group with lowest priority
* first so the group_type can simply be compared when selecting the busiest
* group. See update_sd_pick_busiest().
*/
enum group_type {
/* The group has spare capacity that can be used to run more tasks. */
group_has_spare = 0,
/*
* The group is fully used and the tasks don't compete for more CPU
* cycles. Nevertheless, some tasks might wait before running.
*/
group_fully_busy,
/*
* One task doesn't fit with CPU's capacity and must be migrated to a
* more powerful CPU.
*/
group_misfit_task,
/*
* SD_ASYM_PACKING only: One local CPU with higher capacity is available,
* and the task should be migrated to it instead of running on the
* current CPU.
*/
group_asym_packing,
/*
* The tasks' affinity constraints previously prevented the scheduler
* from balancing the load across the system.
*/
group_imbalanced,
/*
* The CPU is overloaded and can't provide expected CPU cycles to all
* tasks.
*/
group_overloaded
};
enum migration_type {
migrate_load = 0,
migrate_util,
migrate_task,
migrate_misfit
};
#define LBF_ALL_PINNED 0x01
#define LBF_NEED_BREAK 0x02
#define LBF_DST_PINNED 0x04
#define LBF_SOME_PINNED 0x08
#define LBF_ACTIVE_LB 0x10
struct lb_env {
struct sched_domain *sd;
struct rq *src_rq;
int src_cpu;
int dst_cpu;
struct rq *dst_rq;
struct cpumask *dst_grpmask;
int new_dst_cpu;
enum cpu_idle_type idle;
long imbalance;
/* The set of CPUs under consideration for load-balancing */
struct cpumask *cpus;
unsigned int flags;
unsigned int loop;
unsigned int loop_break;
unsigned int loop_max;
enum fbq_type fbq_type;
enum migration_type migration_type;
struct list_head tasks;
};
/*
* Is this task likely cache-hot:
*/
static int task_hot(struct task_struct *p, struct lb_env *env)
{
s64 delta;
lockdep_assert_rq_held(env->src_rq);
if (p->sched_class != &fair_sched_class)
return 0;
if (unlikely(task_has_idle_policy(p)))
return 0;
/* SMT siblings share cache */
if (env->sd->flags & SD_SHARE_CPUCAPACITY)
return 0;
/*
* Buddy candidates are cache hot:
*/
if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
(&p->se == cfs_rq_of(&p->se)->next ||
&p->se == cfs_rq_of(&p->se)->last))
return 1;
if (sysctl_sched_migration_cost == -1)
return 1;
/*
* Don't migrate task if the task's cookie does not match
* with the destination CPU's core cookie.
*/
if (!sched_core_cookie_match(cpu_rq(env->dst_cpu), p))
return 1;
if (sysctl_sched_migration_cost == 0)
return 0;
delta = rq_clock_task(env->src_rq) - p->se.exec_start;
return delta < (s64)sysctl_sched_migration_cost;
}
#ifdef CONFIG_NUMA_BALANCING
/*
* Returns 1, if task migration degrades locality
* Returns 0, if task migration improves locality i.e migration preferred.
* Returns -1, if task migration is not affected by locality.
*/
static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
{
struct numa_group *numa_group = rcu_dereference(p->numa_group);
unsigned long src_weight, dst_weight;
int src_nid, dst_nid, dist;
if (!static_branch_likely(&sched_numa_balancing))
return -1;
if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
return -1;
src_nid = cpu_to_node(env->src_cpu);
dst_nid = cpu_to_node(env->dst_cpu);
if (src_nid == dst_nid)
return -1;
/* Migrating away from the preferred node is always bad. */
if (src_nid == p->numa_preferred_nid) {
if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
return 1;
else
return -1;
}
/* Encourage migration to the preferred node. */
if (dst_nid == p->numa_preferred_nid)
return 0;
/* Leaving a core idle is often worse than degrading locality. */
if (env->idle == CPU_IDLE)
return -1;
dist = node_distance(src_nid, dst_nid);
if (numa_group) {
src_weight = group_weight(p, src_nid, dist);
dst_weight = group_weight(p, dst_nid, dist);
} else {
src_weight = task_weight(p, src_nid, dist);
dst_weight = task_weight(p, dst_nid, dist);
}
return dst_weight < src_weight;
}
#else
static inline int migrate_degrades_locality(struct task_struct *p,
struct lb_env *env)
{
return -1;
}
#endif
/*
* can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
*/
static
int can_migrate_task(struct task_struct *p, struct lb_env *env)
{
int tsk_cache_hot;
lockdep_assert_rq_held(env->src_rq);
/*
* We do not migrate tasks that are:
* 1) throttled_lb_pair, or
* 2) cannot be migrated to this CPU due to cpus_ptr, or
* 3) running (obviously), or
* 4) are cache-hot on their current CPU.
*/
if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
return 0;
/* Disregard pcpu kthreads; they are where they need to be. */
if (kthread_is_per_cpu(p))
return 0;
if (!cpumask_test_cpu(env->dst_cpu, p->cpus_ptr)) {
int cpu;
schedstat_inc(p->stats.nr_failed_migrations_affine);
env->flags |= LBF_SOME_PINNED;
/*
* Remember if this task can be migrated to any other CPU in
* our sched_group. We may want to revisit it if we couldn't
* meet load balance goals by pulling other tasks on src_cpu.
*
* Avoid computing new_dst_cpu
* - for NEWLY_IDLE
* - if we have already computed one in current iteration
* - if it's an active balance
*/
if (env->idle == CPU_NEWLY_IDLE ||
env->flags & (LBF_DST_PINNED | LBF_ACTIVE_LB))
return 0;
/* Prevent to re-select dst_cpu via env's CPUs: */
for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
if (cpumask_test_cpu(cpu, p->cpus_ptr)) {
env->flags |= LBF_DST_PINNED;
env->new_dst_cpu = cpu;
break;
}
}
return 0;
}
/* Record that we found at least one task that could run on dst_cpu */
env->flags &= ~LBF_ALL_PINNED;
if (task_on_cpu(env->src_rq, p)) {
schedstat_inc(p->stats.nr_failed_migrations_running);
return 0;
}
/*
* Aggressive migration if:
* 1) active balance
* 2) destination numa is preferred
* 3) task is cache cold, or
* 4) too many balance attempts have failed.
*/
if (env->flags & LBF_ACTIVE_LB)
return 1;
tsk_cache_hot = migrate_degrades_locality(p, env);
if (tsk_cache_hot == -1)
tsk_cache_hot = task_hot(p, env);
if (tsk_cache_hot <= 0 ||
env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
if (tsk_cache_hot == 1) {
schedstat_inc(env->sd->lb_hot_gained[env->idle]);
schedstat_inc(p->stats.nr_forced_migrations);
}
return 1;
}
schedstat_inc(p->stats.nr_failed_migrations_hot);
return 0;
}
/*
* detach_task() -- detach the task for the migration specified in env
*/
static void detach_task(struct task_struct *p, struct lb_env *env)
{
lockdep_assert_rq_held(env->src_rq);
deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK);
set_task_cpu(p, env->dst_cpu);
}
/*
* detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
* part of active balancing operations within "domain".
*
* Returns a task if successful and NULL otherwise.
*/
static struct task_struct *detach_one_task(struct lb_env *env)
{
struct task_struct *p;
lockdep_assert_rq_held(env->src_rq);
list_for_each_entry_reverse(p,
&env->src_rq->cfs_tasks, se.group_node) {
if (!can_migrate_task(p, env))
continue;
detach_task(p, env);
/*
* Right now, this is only the second place where
* lb_gained[env->idle] is updated (other is detach_tasks)
* so we can safely collect stats here rather than
* inside detach_tasks().
*/
schedstat_inc(env->sd->lb_gained[env->idle]);
return p;
}
return NULL;
}
/*
* detach_tasks() -- tries to detach up to imbalance load/util/tasks from
* busiest_rq, as part of a balancing operation within domain "sd".
*
* Returns number of detached tasks if successful and 0 otherwise.
*/
static int detach_tasks(struct lb_env *env)
{
struct list_head *tasks = &env->src_rq->cfs_tasks;
unsigned long util, load;
struct task_struct *p;
int detached = 0;
lockdep_assert_rq_held(env->src_rq);
/*
* Source run queue has been emptied by another CPU, clear
* LBF_ALL_PINNED flag as we will not test any task.
*/
if (env->src_rq->nr_running <= 1) {
env->flags &= ~LBF_ALL_PINNED;
return 0;
}
if (env->imbalance <= 0)
return 0;
while (!list_empty(tasks)) {
/*
* We don't want to steal all, otherwise we may be treated likewise,
* which could at worst lead to a livelock crash.
*/
if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
break;
env->loop++;
/*
* We've more or less seen every task there is, call it quits
* unless we haven't found any movable task yet.
*/
if (env->loop > env->loop_max &&
!(env->flags & LBF_ALL_PINNED))
break;
/* take a breather every nr_migrate tasks */
if (env->loop > env->loop_break) {
env->loop_break += SCHED_NR_MIGRATE_BREAK;
env->flags |= LBF_NEED_BREAK;
break;
}
p = list_last_entry(tasks, struct task_struct, se.group_node);
if (!can_migrate_task(p, env))
goto next;
switch (env->migration_type) {
case migrate_load:
/*
* Depending of the number of CPUs and tasks and the
* cgroup hierarchy, task_h_load() can return a null
* value. Make sure that env->imbalance decreases
* otherwise detach_tasks() will stop only after
* detaching up to loop_max tasks.
*/
load = max_t(unsigned long, task_h_load(p), 1);
if (sched_feat(LB_MIN) &&
load < 16 && !env->sd->nr_balance_failed)
goto next;
/*
* Make sure that we don't migrate too much load.
* Nevertheless, let relax the constraint if
* scheduler fails to find a good waiting task to
* migrate.
*/
if (shr_bound(load, env->sd->nr_balance_failed) > env->imbalance)
goto next;
env->imbalance -= load;
break;
case migrate_util:
util = task_util_est(p);
if (util > env->imbalance)
goto next;
env->imbalance -= util;
break;
case migrate_task:
env->imbalance--;
break;
case migrate_misfit:
/* This is not a misfit task */
if (task_fits_cpu(p, env->src_cpu))
goto next;
env->imbalance = 0;
break;
}
detach_task(p, env);
list_add(&p->se.group_node, &env->tasks);
detached++;
#ifdef CONFIG_PREEMPTION
/*
* NEWIDLE balancing is a source of latency, so preemptible
* kernels will stop after the first task is detached to minimize
* the critical section.
*/
if (env->idle == CPU_NEWLY_IDLE)
break;
#endif
/*
* We only want to steal up to the prescribed amount of
* load/util/tasks.
*/
if (env->imbalance <= 0)
break;
continue;
next:
list_move(&p->se.group_node, tasks);
}
/*
* Right now, this is one of only two places we collect this stat
* so we can safely collect detach_one_task() stats here rather
* than inside detach_one_task().
*/
schedstat_add(env->sd->lb_gained[env->idle], detached);
return detached;
}
/*
* attach_task() -- attach the task detached by detach_task() to its new rq.
*/
static void attach_task(struct rq *rq, struct task_struct *p)
{
lockdep_assert_rq_held(rq);
WARN_ON_ONCE(task_rq(p) != rq);
activate_task(rq, p, ENQUEUE_NOCLOCK);
check_preempt_curr(rq, p, 0);
}
/*
* attach_one_task() -- attaches the task returned from detach_one_task() to
* its new rq.
*/
static void attach_one_task(struct rq *rq, struct task_struct *p)
{
struct rq_flags rf;
rq_lock(rq, &rf);
update_rq_clock(rq);
attach_task(rq, p);
rq_unlock(rq, &rf);
}
/*
* attach_tasks() -- attaches all tasks detached by detach_tasks() to their
* new rq.
*/
static void attach_tasks(struct lb_env *env)
{
struct list_head *tasks = &env->tasks;
struct task_struct *p;
struct rq_flags rf;
rq_lock(env->dst_rq, &rf);
update_rq_clock(env->dst_rq);
while (!list_empty(tasks)) {
p = list_first_entry(tasks, struct task_struct, se.group_node);
list_del_init(&p->se.group_node);
attach_task(env->dst_rq, p);
}
rq_unlock(env->dst_rq, &rf);
}
#ifdef CONFIG_NO_HZ_COMMON
static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq)
{
if (cfs_rq->avg.load_avg)
return true;
if (cfs_rq->avg.util_avg)
return true;
return false;
}
static inline bool others_have_blocked(struct rq *rq)
{
if (READ_ONCE(rq->avg_rt.util_avg))
return true;
if (READ_ONCE(rq->avg_dl.util_avg))
return true;
if (thermal_load_avg(rq))
return true;
#ifdef CONFIG_HAVE_SCHED_AVG_IRQ
if (READ_ONCE(rq->avg_irq.util_avg))
return true;
#endif
return false;
}
static inline void update_blocked_load_tick(struct rq *rq)
{
WRITE_ONCE(rq->last_blocked_load_update_tick, jiffies);
}
static inline void update_blocked_load_status(struct rq *rq, bool has_blocked)
{
if (!has_blocked)
rq->has_blocked_load = 0;
}
#else
static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq) { return false; }
static inline bool others_have_blocked(struct rq *rq) { return false; }
static inline void update_blocked_load_tick(struct rq *rq) {}
static inline void update_blocked_load_status(struct rq *rq, bool has_blocked) {}
#endif
static bool __update_blocked_others(struct rq *rq, bool *done)
{
const struct sched_class *curr_class;
u64 now = rq_clock_pelt(rq);
unsigned long thermal_pressure;
bool decayed;
/*
* update_load_avg() can call cpufreq_update_util(). Make sure that RT,
* DL and IRQ signals have been updated before updating CFS.
*/
curr_class = rq->curr->sched_class;
thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq));
decayed = update_rt_rq_load_avg(now, rq, curr_class == &rt_sched_class) |
update_dl_rq_load_avg(now, rq, curr_class == &dl_sched_class) |
update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure) |
update_irq_load_avg(rq, 0);
if (others_have_blocked(rq))
*done = false;
return decayed;
}
#ifdef CONFIG_FAIR_GROUP_SCHED
static bool __update_blocked_fair(struct rq *rq, bool *done)
{
struct cfs_rq *cfs_rq, *pos;
bool decayed = false;
int cpu = cpu_of(rq);
/*
* Iterates the task_group tree in a bottom up fashion, see
* list_add_leaf_cfs_rq() for details.
*/
for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) {
struct sched_entity *se;
if (update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq)) {
update_tg_load_avg(cfs_rq);
if (cfs_rq->nr_running == 0)
update_idle_cfs_rq_clock_pelt(cfs_rq);
if (cfs_rq == &rq->cfs)
decayed = true;
}
/* Propagate pending load changes to the parent, if any: */
se = cfs_rq->tg->se[cpu];
if (se && !skip_blocked_update(se))
update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
/*
* There can be a lot of idle CPU cgroups. Don't let fully
* decayed cfs_rqs linger on the list.
*/
if (cfs_rq_is_decayed(cfs_rq))
list_del_leaf_cfs_rq(cfs_rq);
/* Don't need periodic decay once load/util_avg are null */
if (cfs_rq_has_blocked(cfs_rq))
*done = false;
}
return decayed;
}
/*
* Compute the hierarchical load factor for cfs_rq and all its ascendants.
* This needs to be done in a top-down fashion because the load of a child
* group is a fraction of its parents load.
*/
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
{
struct rq *rq = rq_of(cfs_rq);
struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
unsigned long now = jiffies;
unsigned long load;
if (cfs_rq->last_h_load_update == now)
return;
WRITE_ONCE(cfs_rq->h_load_next, NULL);
for_each_sched_entity(se) {
cfs_rq = cfs_rq_of(se);
WRITE_ONCE(cfs_rq->h_load_next, se);
if (cfs_rq->last_h_load_update == now)
break;
}
if (!se) {
cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
cfs_rq->last_h_load_update = now;
}
while ((se = READ_ONCE(cfs_rq->h_load_next)) != NULL) {
load = cfs_rq->h_load;
load = div64_ul(load * se->avg.load_avg,
cfs_rq_load_avg(cfs_rq) + 1);
cfs_rq = group_cfs_rq(se);
cfs_rq->h_load = load;
cfs_rq->last_h_load_update = now;
}
}
static unsigned long task_h_load(struct task_struct *p)
{
struct cfs_rq *cfs_rq = task_cfs_rq(p);
update_cfs_rq_h_load(cfs_rq);
return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
cfs_rq_load_avg(cfs_rq) + 1);
}
#else
static bool __update_blocked_fair(struct rq *rq, bool *done)
{
struct cfs_rq *cfs_rq = &rq->cfs;
bool decayed;
decayed = update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq);
if (cfs_rq_has_blocked(cfs_rq))
*done = false;
return decayed;
}
static unsigned long task_h_load(struct task_struct *p)
{
return p->se.avg.load_avg;
}
#endif
static void update_blocked_averages(int cpu)
{
bool decayed = false, done = true;
struct rq *rq = cpu_rq(cpu);
struct rq_flags rf;
rq_lock_irqsave(rq, &rf);
update_blocked_load_tick(rq);
update_rq_clock(rq);
decayed |= __update_blocked_others(rq, &done);
decayed |= __update_blocked_fair(rq, &done);
update_blocked_load_status(rq, !done);
if (decayed)
cpufreq_update_util(rq, 0);
rq_unlock_irqrestore(rq, &rf);
}
/********** Helpers for find_busiest_group ************************/
/*
* sg_lb_stats - stats of a sched_group required for load_balancing
*/
struct sg_lb_stats {
unsigned long avg_load; /*Avg load across the CPUs of the group */
unsigned long group_load; /* Total load over the CPUs of the group */
unsigned long group_capacity;
unsigned long group_util; /* Total utilization over the CPUs of the group */
unsigned long group_runnable; /* Total runnable time over the CPUs of the group */
unsigned int sum_nr_running; /* Nr of tasks running in the group */
unsigned int sum_h_nr_running; /* Nr of CFS tasks running in the group */
unsigned int idle_cpus;
unsigned int group_weight;
enum group_type group_type;
unsigned int group_asym_packing; /* Tasks should be moved to preferred CPU */
unsigned long group_misfit_task_load; /* A CPU has a task too big for its capacity */
#ifdef CONFIG_NUMA_BALANCING
unsigned int nr_numa_running;
unsigned int nr_preferred_running;
#endif
};
/*
* sd_lb_stats - Structure to store the statistics of a sched_domain
* during load balancing.
*/
struct sd_lb_stats {
struct sched_group *busiest; /* Busiest group in this sd */
struct sched_group *local; /* Local group in this sd */
unsigned long total_load; /* Total load of all groups in sd */
unsigned long total_capacity; /* Total capacity of all groups in sd */
unsigned long avg_load; /* Average load across all groups in sd */
unsigned int prefer_sibling; /* tasks should go to sibling first */
struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
struct sg_lb_stats local_stat; /* Statistics of the local group */
};
static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
{
/*
* Skimp on the clearing to avoid duplicate work. We can avoid clearing
* local_stat because update_sg_lb_stats() does a full clear/assignment.
* We must however set busiest_stat::group_type and
* busiest_stat::idle_cpus to the worst busiest group because
* update_sd_pick_busiest() reads these before assignment.
*/
*sds = (struct sd_lb_stats){
.busiest = NULL,
.local = NULL,
.total_load = 0UL,
.total_capacity = 0UL,
.busiest_stat = {
.idle_cpus = UINT_MAX,
.group_type = group_has_spare,
},
};
}
static unsigned long scale_rt_capacity(int cpu)
{
struct rq *rq = cpu_rq(cpu);
unsigned long max = arch_scale_cpu_capacity(cpu);
unsigned long used, free;
unsigned long irq;
irq = cpu_util_irq(rq);
if (unlikely(irq >= max))
return 1;
/*
* avg_rt.util_avg and avg_dl.util_avg track binary signals
* (running and not running) with weights 0 and 1024 respectively.
* avg_thermal.load_avg tracks thermal pressure and the weighted
* average uses the actual delta max capacity(load).
*/
used = READ_ONCE(rq->avg_rt.util_avg);
used += READ_ONCE(rq->avg_dl.util_avg);
used += thermal_load_avg(rq);
if (unlikely(used >= max))
return 1;
free = max - used;
return scale_irq_capacity(free, irq, max);
}
static void update_cpu_capacity(struct sched_domain *sd, int cpu)
{
unsigned long capacity = scale_rt_capacity(cpu);
struct sched_group *sdg = sd->groups;
cpu_rq(cpu)->cpu_capacity_orig = arch_scale_cpu_capacity(cpu);
if (!capacity)
capacity = 1;
cpu_rq(cpu)->cpu_capacity = capacity;
trace_sched_cpu_capacity_tp(cpu_rq(cpu));
sdg->sgc->capacity = capacity;
sdg->sgc->min_capacity = capacity;
sdg->sgc->max_capacity = capacity;
}
void update_group_capacity(struct sched_domain *sd, int cpu)
{
struct sched_domain *child = sd->child;
struct sched_group *group, *sdg = sd->groups;
unsigned long capacity, min_capacity, max_capacity;
unsigned long interval;
interval = msecs_to_jiffies(sd->balance_interval);
interval = clamp(interval, 1UL, max_load_balance_interval);
sdg->sgc->next_update = jiffies + interval;
if (!child) {
update_cpu_capacity(sd, cpu);
return;
}
capacity = 0;
min_capacity = ULONG_MAX;
max_capacity = 0;
if (child->flags & SD_OVERLAP) {
/*
* SD_OVERLAP domains cannot assume that child groups
* span the current group.
*/
for_each_cpu(cpu, sched_group_span(sdg)) {
unsigned long cpu_cap = capacity_of(cpu);
capacity += cpu_cap;
min_capacity = min(cpu_cap, min_capacity);
max_capacity = max(cpu_cap, max_capacity);
}
} else {
/*
* !SD_OVERLAP domains can assume that child groups
* span the current group.
*/
group = child->groups;
do {
struct sched_group_capacity *sgc = group->sgc;
capacity += sgc->capacity;
min_capacity = min(sgc->min_capacity, min_capacity);
max_capacity = max(sgc->max_capacity, max_capacity);
group = group->next;
} while (group != child->groups);
}
sdg->sgc->capacity = capacity;
sdg->sgc->min_capacity = min_capacity;
sdg->sgc->max_capacity = max_capacity;
}
/*
* Check whether the capacity of the rq has been noticeably reduced by side
* activity. The imbalance_pct is used for the threshold.
* Return true is the capacity is reduced
*/
static inline int
check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
{
return ((rq->cpu_capacity * sd->imbalance_pct) <
(rq->cpu_capacity_orig * 100));
}
/*
* Check whether a rq has a misfit task and if it looks like we can actually
* help that task: we can migrate the task to a CPU of higher capacity, or
* the task's current CPU is heavily pressured.
*/
static inline int check_misfit_status(struct rq *rq, struct sched_domain *sd)
{
return rq->misfit_task_load &&
(rq->cpu_capacity_orig < rq->rd->max_cpu_capacity ||
check_cpu_capacity(rq, sd));
}
/*
* Group imbalance indicates (and tries to solve) the problem where balancing
* groups is inadequate due to ->cpus_ptr constraints.
*
* Imagine a situation of two groups of 4 CPUs each and 4 tasks each with a
* cpumask covering 1 CPU of the first group and 3 CPUs of the second group.
* Something like:
*
* { 0 1 2 3 } { 4 5 6 7 }
* * * * *
*
* If we were to balance group-wise we'd place two tasks in the first group and
* two tasks in the second group. Clearly this is undesired as it will overload
* cpu 3 and leave one of the CPUs in the second group unused.
*
* The current solution to this issue is detecting the skew in the first group
* by noticing the lower domain failed to reach balance and had difficulty
* moving tasks due to affinity constraints.
*
* When this is so detected; this group becomes a candidate for busiest; see
* update_sd_pick_busiest(). And calculate_imbalance() and
* find_busiest_group() avoid some of the usual balance conditions to allow it
* to create an effective group imbalance.
*
* This is a somewhat tricky proposition since the next run might not find the
* group imbalance and decide the groups need to be balanced again. A most
* subtle and fragile situation.
*/
static inline int sg_imbalanced(struct sched_group *group)
{
return group->sgc->imbalance;
}
/*
* group_has_capacity returns true if the group has spare capacity that could
* be used by some tasks.
* We consider that a group has spare capacity if the number of task is
* smaller than the number of CPUs or if the utilization is lower than the
* available capacity for CFS tasks.
* For the latter, we use a threshold to stabilize the state, to take into
* account the variance of the tasks' load and to return true if the available
* capacity in meaningful for the load balancer.
* As an example, an available capacity of 1% can appear but it doesn't make
* any benefit for the load balance.
*/
static inline bool
group_has_capacity(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
{
if (sgs->sum_nr_running < sgs->group_weight)
return true;
if ((sgs->group_capacity * imbalance_pct) <
(sgs->group_runnable * 100))
return false;
if ((sgs->group_capacity * 100) >
(sgs->group_util * imbalance_pct))
return true;
return false;
}
/*
* group_is_overloaded returns true if the group has more tasks than it can
* handle.
* group_is_overloaded is not equals to !group_has_capacity because a group
* with the exact right number of tasks, has no more spare capacity but is not
* overloaded so both group_has_capacity and group_is_overloaded return
* false.
*/
static inline bool
group_is_overloaded(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
{
if (sgs->sum_nr_running <= sgs->group_weight)
return false;
if ((sgs->group_capacity * 100) <
(sgs->group_util * imbalance_pct))
return true;
if ((sgs->group_capacity * imbalance_pct) <
(sgs->group_runnable * 100))
return true;
return false;
}
static inline enum
group_type group_classify(unsigned int imbalance_pct,
struct sched_group *group,
struct sg_lb_stats *sgs)
{
if (group_is_overloaded(imbalance_pct, sgs))
return group_overloaded;
if (sg_imbalanced(group))
return group_imbalanced;
if (sgs->group_asym_packing)
return group_asym_packing;
if (sgs->group_misfit_task_load)
return group_misfit_task;
if (!group_has_capacity(imbalance_pct, sgs))
return group_fully_busy;
return group_has_spare;
}
/**
* sched_use_asym_prio - Check whether asym_packing priority must be used
* @sd: The scheduling domain of the load balancing
* @cpu: A CPU
*
* Always use CPU priority when balancing load between SMT siblings. When
* balancing load between cores, it is not sufficient that @cpu is idle. Only
* use CPU priority if the whole core is idle.
*
* Returns: True if the priority of @cpu must be followed. False otherwise.
*/
static bool sched_use_asym_prio(struct sched_domain *sd, int cpu)
{
if (!sched_smt_active())
return true;
return sd->flags & SD_SHARE_CPUCAPACITY || is_core_idle(cpu);
}
/**
* sched_asym - Check if the destination CPU can do asym_packing load balance
* @env: The load balancing environment
* @sds: Load-balancing data with statistics of the local group
* @sgs: Load-balancing statistics of the candidate busiest group
* @group: The candidate busiest group
*
* @env::dst_cpu can do asym_packing if it has higher priority than the
* preferred CPU of @group.
*
* SMT is a special case. If we are balancing load between cores, @env::dst_cpu
* can do asym_packing balance only if all its SMT siblings are idle. Also, it
* can only do it if @group is an SMT group and has exactly on busy CPU. Larger
* imbalances in the number of CPUS are dealt with in find_busiest_group().
*
* If we are balancing load within an SMT core, or at DIE domain level, always
* proceed.
*
* Return: true if @env::dst_cpu can do with asym_packing load balance. False
* otherwise.
*/
static inline bool
sched_asym(struct lb_env *env, struct sd_lb_stats *sds, struct sg_lb_stats *sgs,
struct sched_group *group)
{
/* Ensure that the whole local core is idle, if applicable. */
if (!sched_use_asym_prio(env->sd, env->dst_cpu))
return false;
/*
* CPU priorities does not make sense for SMT cores with more than one
* busy sibling.
*/
if (group->flags & SD_SHARE_CPUCAPACITY) {
if (sgs->group_weight - sgs->idle_cpus != 1)
return false;
}
return sched_asym_prefer(env->dst_cpu, group->asym_prefer_cpu);
}
static inline bool
sched_reduced_capacity(struct rq *rq, struct sched_domain *sd)
{
/*
* When there is more than 1 task, the group_overloaded case already
* takes care of cpu with reduced capacity
*/
if (rq->cfs.h_nr_running != 1)
return false;
return check_cpu_capacity(rq, sd);
}
/**
* update_sg_lb_stats - Update sched_group's statistics for load balancing.
* @env: The load balancing environment.
* @sds: Load-balancing data with statistics of the local group.
* @group: sched_group whose statistics are to be updated.
* @sgs: variable to hold the statistics for this group.
* @sg_status: Holds flag indicating the status of the sched_group
*/
static inline void update_sg_lb_stats(struct lb_env *env,
struct sd_lb_stats *sds,
struct sched_group *group,
struct sg_lb_stats *sgs,
int *sg_status)
{
int i, nr_running, local_group;
memset(sgs, 0, sizeof(*sgs));
local_group = group == sds->local;
for_each_cpu_and(i, sched_group_span(group), env->cpus) {
struct rq *rq = cpu_rq(i);
unsigned long load = cpu_load(rq);
sgs->group_load += load;
sgs->group_util += cpu_util_cfs(i);
sgs->group_runnable += cpu_runnable(rq);
sgs->sum_h_nr_running += rq->cfs.h_nr_running;
nr_running = rq->nr_running;
sgs->sum_nr_running += nr_running;
if (nr_running > 1)
*sg_status |= SG_OVERLOAD;
if (cpu_overutilized(i))
*sg_status |= SG_OVERUTILIZED;
#ifdef CONFIG_NUMA_BALANCING
sgs->nr_numa_running += rq->nr_numa_running;
sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
/*
* No need to call idle_cpu() if nr_running is not 0
*/
if (!nr_running && idle_cpu(i)) {
sgs->idle_cpus++;
/* Idle cpu can't have misfit task */
continue;
}
if (local_group)
continue;
if (env->sd->flags & SD_ASYM_CPUCAPACITY) {
/* Check for a misfit task on the cpu */
if (sgs->group_misfit_task_load < rq->misfit_task_load) {
sgs->group_misfit_task_load = rq->misfit_task_load;
*sg_status |= SG_OVERLOAD;
}
} else if ((env->idle != CPU_NOT_IDLE) &&
sched_reduced_capacity(rq, env->sd)) {
/* Check for a task running on a CPU with reduced capacity */
if (sgs->group_misfit_task_load < load)
sgs->group_misfit_task_load = load;
}
}
sgs->group_capacity = group->sgc->capacity;
sgs->group_weight = group->group_weight;
/* Check if dst CPU is idle and preferred to this group */
if (!local_group && env->sd->flags & SD_ASYM_PACKING &&
env->idle != CPU_NOT_IDLE && sgs->sum_h_nr_running &&
sched_asym(env, sds, sgs, group)) {
sgs->group_asym_packing = 1;
}
sgs->group_type = group_classify(env->sd->imbalance_pct, group, sgs);
/* Computing avg_load makes sense only when group is overloaded */
if (sgs->group_type == group_overloaded)
sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /
sgs->group_capacity;
}
/**
* update_sd_pick_busiest - return 1 on busiest group
* @env: The load balancing environment.
* @sds: sched_domain statistics
* @sg: sched_group candidate to be checked for being the busiest
* @sgs: sched_group statistics
*
* Determine if @sg is a busier group than the previously selected
* busiest group.
*
* Return: %true if @sg is a busier group than the previously selected
* busiest group. %false otherwise.
*/
static bool update_sd_pick_busiest(struct lb_env *env,
struct sd_lb_stats *sds,
struct sched_group *sg,
struct sg_lb_stats *sgs)
{
struct sg_lb_stats *busiest = &sds->busiest_stat;
/* Make sure that there is at least one task to pull */
if (!sgs->sum_h_nr_running)
return false;
/*
* Don't try to pull misfit tasks we can't help.
* We can use max_capacity here as reduction in capacity on some
* CPUs in the group should either be possible to resolve
* internally or be covered by avg_load imbalance (eventually).
*/
if ((env->sd->flags & SD_ASYM_CPUCAPACITY) &&
(sgs->group_type == group_misfit_task) &&
(!capacity_greater(capacity_of(env->dst_cpu), sg->sgc->max_capacity) ||
sds->local_stat.group_type != group_has_spare))
return false;
if (sgs->group_type > busiest->group_type)
return true;
if (sgs->group_type < busiest->group_type)
return false;
/*
* The candidate and the current busiest group are the same type of
* group. Let check which one is the busiest according to the type.
*/
switch (sgs->group_type) {
case group_overloaded:
/* Select the overloaded group with highest avg_load. */
if (sgs->avg_load <= busiest->avg_load)
return false;
break;
case group_imbalanced:
/*
* Select the 1st imbalanced group as we don't have any way to
* choose one more than another.
*/
return false;
case group_asym_packing:
/* Prefer to move from lowest priority CPU's work */
if (sched_asym_prefer(sg->asym_prefer_cpu, sds->busiest->asym_prefer_cpu))
return false;
break;
case group_misfit_task:
/*
* If we have more than one misfit sg go with the biggest
* misfit.
*/
if (sgs->group_misfit_task_load < busiest->group_misfit_task_load)
return false;
break;
case group_fully_busy:
/*
* Select the fully busy group with highest avg_load. In
* theory, there is no need to pull task from such kind of
* group because tasks have all compute capacity that they need
* but we can still improve the overall throughput by reducing
* contention when accessing shared HW resources.
*
* XXX for now avg_load is not computed and always 0 so we
* select the 1st one, except if @sg is composed of SMT
* siblings.
*/
if (sgs->avg_load < busiest->avg_load)
return false;
if (sgs->avg_load == busiest->avg_load) {
/*
* SMT sched groups need more help than non-SMT groups.
* If @sg happens to also be SMT, either choice is good.
*/
if (sds->busiest->flags & SD_SHARE_CPUCAPACITY)
return false;
}
break;
case group_has_spare:
/*
* Select not overloaded group with lowest number of idle cpus
* and highest number of running tasks. We could also compare
* the spare capacity which is more stable but it can end up
* that the group has less spare capacity but finally more idle
* CPUs which means less opportunity to pull tasks.
*/
if (sgs->idle_cpus > busiest->idle_cpus)
return false;
else if ((sgs->idle_cpus == busiest->idle_cpus) &&
(sgs->sum_nr_running <= busiest->sum_nr_running))
return false;
break;
}
/*
* Candidate sg has no more than one task per CPU and has higher
* per-CPU capacity. Migrating tasks to less capable CPUs may harm
* throughput. Maximize throughput, power/energy consequences are not
* considered.
*/
if ((env->sd->flags & SD_ASYM_CPUCAPACITY) &&
(sgs->group_type <= group_fully_busy) &&
(capacity_greater(sg->sgc->min_capacity, capacity_of(env->dst_cpu))))
return false;
return true;
}
#ifdef CONFIG_NUMA_BALANCING
static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
{
if (sgs->sum_h_nr_running > sgs->nr_numa_running)
return regular;
if (sgs->sum_h_nr_running > sgs->nr_preferred_running)
return remote;
return all;
}
static inline enum fbq_type fbq_classify_rq(struct rq *rq)
{
if (rq->nr_running > rq->nr_numa_running)
return regular;
if (rq->nr_running > rq->nr_preferred_running)
return remote;
return all;
}
#else
static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
{
return all;
}
static inline enum fbq_type fbq_classify_rq(struct rq *rq)
{
return regular;
}
#endif /* CONFIG_NUMA_BALANCING */
struct sg_lb_stats;
/*
* task_running_on_cpu - return 1 if @p is running on @cpu.
*/
static unsigned int task_running_on_cpu(int cpu, struct task_struct *p)
{
/* Task has no contribution or is new */
if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
return 0;
if (task_on_rq_queued(p))
return 1;
return 0;
}
/**
* idle_cpu_without - would a given CPU be idle without p ?
* @cpu: the processor on which idleness is tested.
* @p: task which should be ignored.
*
* Return: 1 if the CPU would be idle. 0 otherwise.
*/
static int idle_cpu_without(int cpu, struct task_struct *p)
{
struct rq *rq = cpu_rq(cpu);
if (rq->curr != rq->idle && rq->curr != p)
return 0;
/*
* rq->nr_running can't be used but an updated version without the
* impact of p on cpu must be used instead. The updated nr_running
* be computed and tested before calling idle_cpu_without().
*/
#ifdef CONFIG_SMP
if (rq->ttwu_pending)
return 0;
#endif
return 1;
}
/*
* update_sg_wakeup_stats - Update sched_group's statistics for wakeup.
* @sd: The sched_domain level to look for idlest group.
* @group: sched_group whose statistics are to be updated.
* @sgs: variable to hold the statistics for this group.
* @p: The task for which we look for the idlest group/CPU.
*/
static inline void update_sg_wakeup_stats(struct sched_domain *sd,
struct sched_group *group,
struct sg_lb_stats *sgs,
struct task_struct *p)
{
int i, nr_running;
memset(sgs, 0, sizeof(*sgs));
/* Assume that task can't fit any CPU of the group */
if (sd->flags & SD_ASYM_CPUCAPACITY)
sgs->group_misfit_task_load = 1;
for_each_cpu(i, sched_group_span(group)) {
struct rq *rq = cpu_rq(i);
unsigned int local;
sgs->group_load += cpu_load_without(rq, p);
sgs->group_util += cpu_util_without(i, p);
sgs->group_runnable += cpu_runnable_without(rq, p);
local = task_running_on_cpu(i, p);
sgs->sum_h_nr_running += rq->cfs.h_nr_running - local;
nr_running = rq->nr_running - local;
sgs->sum_nr_running += nr_running;
/*
* No need to call idle_cpu_without() if nr_running is not 0
*/
if (!nr_running && idle_cpu_without(i, p))
sgs->idle_cpus++;
/* Check if task fits in the CPU */
if (sd->flags & SD_ASYM_CPUCAPACITY &&
sgs->group_misfit_task_load &&
task_fits_cpu(p, i))
sgs->group_misfit_task_load = 0;
}
sgs->group_capacity = group->sgc->capacity;
sgs->group_weight = group->group_weight;
sgs->group_type = group_classify(sd->imbalance_pct, group, sgs);
/*
* Computing avg_load makes sense only when group is fully busy or
* overloaded
*/
if (sgs->group_type == group_fully_busy ||
sgs->group_type == group_overloaded)
sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /
sgs->group_capacity;
}
static bool update_pick_idlest(struct sched_group *idlest,
struct sg_lb_stats *idlest_sgs,
struct sched_group *group,
struct sg_lb_stats *sgs)
{
if (sgs->group_type < idlest_sgs->group_type)
return true;
if (sgs->group_type > idlest_sgs->group_type)
return false;
/*
* The candidate and the current idlest group are the same type of
* group. Let check which one is the idlest according to the type.
*/
switch (sgs->group_type) {
case group_overloaded:
case group_fully_busy:
/* Select the group with lowest avg_load. */
if (idlest_sgs->avg_load <= sgs->avg_load)
return false;
break;
case group_imbalanced:
case group_asym_packing:
/* Those types are not used in the slow wakeup path */
return false;
case group_misfit_task:
/* Select group with the highest max capacity */
if (idlest->sgc->max_capacity >= group->sgc->max_capacity)
return false;
break;
case group_has_spare:
/* Select group with most idle CPUs */
if (idlest_sgs->idle_cpus > sgs->idle_cpus)
return false;
/* Select group with lowest group_util */
if (idlest_sgs->idle_cpus == sgs->idle_cpus &&
idlest_sgs->group_util <= sgs->group_util)
return false;
break;
}
return true;
}
/*
* find_idlest_group() finds and returns the least busy CPU group within the
* domain.
*
* Assumes p is allowed on at least one CPU in sd.
*/
static struct sched_group *
find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
{
struct sched_group *idlest = NULL, *local = NULL, *group = sd->groups;
struct sg_lb_stats local_sgs, tmp_sgs;
struct sg_lb_stats *sgs;
unsigned long imbalance;
struct sg_lb_stats idlest_sgs = {
.avg_load = UINT_MAX,
.group_type = group_overloaded,
};
do {
int local_group;
/* Skip over this group if it has no CPUs allowed */
if (!cpumask_intersects(sched_group_span(group),
p->cpus_ptr))
continue;
/* Skip over this group if no cookie matched */
if (!sched_group_cookie_match(cpu_rq(this_cpu), p, group))
continue;
local_group = cpumask_test_cpu(this_cpu,
sched_group_span(group));
if (local_group) {
sgs = &local_sgs;
local = group;
} else {
sgs = &tmp_sgs;
}
update_sg_wakeup_stats(sd, group, sgs, p);
if (!local_group && update_pick_idlest(idlest, &idlest_sgs, group, sgs)) {
idlest = group;
idlest_sgs = *sgs;
}
} while (group = group->next, group != sd->groups);
/* There is no idlest group to push tasks to */
if (!idlest)
return NULL;
/* The local group has been skipped because of CPU affinity */
if (!local)
return idlest;
/*
* If the local group is idler than the selected idlest group
* don't try and push the task.
*/
if (local_sgs.group_type < idlest_sgs.group_type)
return NULL;
/*
* If the local group is busier than the selected idlest group
* try and push the task.
*/
if (local_sgs.group_type > idlest_sgs.group_type)
return idlest;
switch (local_sgs.group_type) {
case group_overloaded:
case group_fully_busy:
/* Calculate allowed imbalance based on load */
imbalance = scale_load_down(NICE_0_LOAD) *
(sd->imbalance_pct-100) / 100;
/*
* When comparing groups across NUMA domains, it's possible for
* the local domain to be very lightly loaded relative to the
* remote domains but "imbalance" skews the comparison making
* remote CPUs look much more favourable. When considering
* cross-domain, add imbalance to the load on the remote node
* and consider staying local.
*/
if ((sd->flags & SD_NUMA) &&
((idlest_sgs.avg_load + imbalance) >= local_sgs.avg_load))
return NULL;
/*
* If the local group is less loaded than the selected
* idlest group don't try and push any tasks.
*/
if (idlest_sgs.avg_load >= (local_sgs.avg_load + imbalance))
return NULL;
if (100 * local_sgs.avg_load <= sd->imbalance_pct * idlest_sgs.avg_load)
return NULL;
break;
case group_imbalanced:
case group_asym_packing:
/* Those type are not used in the slow wakeup path */
return NULL;
case group_misfit_task:
/* Select group with the highest max capacity */
if (local->sgc->max_capacity >= idlest->sgc->max_capacity)
return NULL;
break;
case group_has_spare:
#ifdef CONFIG_NUMA
if (sd->flags & SD_NUMA) {
int imb_numa_nr = sd->imb_numa_nr;
#ifdef CONFIG_NUMA_BALANCING
int idlest_cpu;
/*
* If there is spare capacity at NUMA, try to select
* the preferred node
*/
if (cpu_to_node(this_cpu) == p->numa_preferred_nid)
return NULL;
idlest_cpu = cpumask_first(sched_group_span(idlest));
if (cpu_to_node(idlest_cpu) == p->numa_preferred_nid)
return idlest;
#endif /* CONFIG_NUMA_BALANCING */
/*
* Otherwise, keep the task close to the wakeup source
* and improve locality if the number of running tasks
* would remain below threshold where an imbalance is
* allowed while accounting for the possibility the
* task is pinned to a subset of CPUs. If there is a
* real need of migration, periodic load balance will
* take care of it.
*/
if (p->nr_cpus_allowed != NR_CPUS) {
struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_rq_mask);
cpumask_and(cpus, sched_group_span(local), p->cpus_ptr);
imb_numa_nr = min(cpumask_weight(cpus), sd->imb_numa_nr);
}
imbalance = abs(local_sgs.idle_cpus - idlest_sgs.idle_cpus);
if (!adjust_numa_imbalance(imbalance,
local_sgs.sum_nr_running + 1,
imb_numa_nr)) {
return NULL;
}
}
#endif /* CONFIG_NUMA */
/*
* Select group with highest number of idle CPUs. We could also
* compare the utilization which is more stable but it can end
* up that the group has less spare capacity but finally more
* idle CPUs which means more opportunity to run task.
*/
if (local_sgs.idle_cpus >= idlest_sgs.idle_cpus)
return NULL;
break;
}
return idlest;
}
static void update_idle_cpu_scan(struct lb_env *env,
unsigned long sum_util)
{
struct sched_domain_shared *sd_share;
int llc_weight, pct;
u64 x, y, tmp;
/*
* Update the number of CPUs to scan in LLC domain, which could
* be used as a hint in select_idle_cpu(). The update of sd_share
* could be expensive because it is within a shared cache line.
* So the write of this hint only occurs during periodic load
* balancing, rather than CPU_NEWLY_IDLE, because the latter
* can fire way more frequently than the former.
*/
if (!sched_feat(SIS_UTIL) || env->idle == CPU_NEWLY_IDLE)
return;
llc_weight = per_cpu(sd_llc_size, env->dst_cpu);
if (env->sd->span_weight != llc_weight)
return;
sd_share = rcu_dereference(per_cpu(sd_llc_shared, env->dst_cpu));
if (!sd_share)
return;
/*
* The number of CPUs to search drops as sum_util increases, when
* sum_util hits 85% or above, the scan stops.
* The reason to choose 85% as the threshold is because this is the
* imbalance_pct(117) when a LLC sched group is overloaded.
*
* let y = SCHED_CAPACITY_SCALE - p * x^2 [1]
* and y'= y / SCHED_CAPACITY_SCALE
*
* x is the ratio of sum_util compared to the CPU capacity:
* x = sum_util / (llc_weight * SCHED_CAPACITY_SCALE)
* y' is the ratio of CPUs to be scanned in the LLC domain,
* and the number of CPUs to scan is calculated by:
*
* nr_scan = llc_weight * y' [2]
*
* When x hits the threshold of overloaded, AKA, when
* x = 100 / pct, y drops to 0. According to [1],
* p should be SCHED_CAPACITY_SCALE * pct^2 / 10000
*
* Scale x by SCHED_CAPACITY_SCALE:
* x' = sum_util / llc_weight; [3]
*
* and finally [1] becomes:
* y = SCHED_CAPACITY_SCALE -
* x'^2 * pct^2 / (10000 * SCHED_CAPACITY_SCALE) [4]
*
*/
/* equation [3] */
x = sum_util;
do_div(x, llc_weight);
/* equation [4] */
pct = env->sd->imbalance_pct;
tmp = x * x * pct * pct;
do_div(tmp, 10000 * SCHED_CAPACITY_SCALE);
tmp = min_t(long, tmp, SCHED_CAPACITY_SCALE);
y = SCHED_CAPACITY_SCALE - tmp;
/* equation [2] */
y *= llc_weight;
do_div(y, SCHED_CAPACITY_SCALE);
if ((int)y != sd_share->nr_idle_scan)
WRITE_ONCE(sd_share->nr_idle_scan, (int)y);
}
/**
* update_sd_lb_stats - Update sched_domain's statistics for load balancing.
* @env: The load balancing environment.
* @sds: variable to hold the statistics for this sched_domain.
*/
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
{
struct sched_group *sg = env->sd->groups;
struct sg_lb_stats *local = &sds->local_stat;
struct sg_lb_stats tmp_sgs;
unsigned long sum_util = 0;
int sg_status = 0;
do {
struct sg_lb_stats *sgs = &tmp_sgs;
int local_group;
local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sg));
if (local_group) {
sds->local = sg;
sgs = local;
if (env->idle != CPU_NEWLY_IDLE ||
time_after_eq(jiffies, sg->sgc->next_update))
update_group_capacity(env->sd, env->dst_cpu);
}
update_sg_lb_stats(env, sds, sg, sgs, &sg_status);
if (local_group)
goto next_group;
if (update_sd_pick_busiest(env, sds, sg, sgs)) {
sds->busiest = sg;
sds->busiest_stat = *sgs;
}
next_group:
/* Now, start updating sd_lb_stats */
sds->total_load += sgs->group_load;
sds->total_capacity += sgs->group_capacity;
sum_util += sgs->group_util;
sg = sg->next;
} while (sg != env->sd->groups);
/*
* Indicate that the child domain of the busiest group prefers tasks
* go to a child's sibling domains first. NB the flags of a sched group
* are those of the child domain.
*/
if (sds->busiest)
sds->prefer_sibling = !!(sds->busiest->flags & SD_PREFER_SIBLING);
if (env->sd->flags & SD_NUMA)
env->fbq_type = fbq_classify_group(&sds->busiest_stat);
if (!env->sd->parent) {
struct root_domain *rd = env->dst_rq->rd;
/* update overload indicator if we are at root domain */
WRITE_ONCE(rd->overload, sg_status & SG_OVERLOAD);
/* Update over-utilization (tipping point, U >= 0) indicator */
WRITE_ONCE(rd->overutilized, sg_status & SG_OVERUTILIZED);
trace_sched_overutilized_tp(rd, sg_status & SG_OVERUTILIZED);
} else if (sg_status & SG_OVERUTILIZED) {
struct root_domain *rd = env->dst_rq->rd;
WRITE_ONCE(rd->overutilized, SG_OVERUTILIZED);
trace_sched_overutilized_tp(rd, SG_OVERUTILIZED);
}
update_idle_cpu_scan(env, sum_util);
}
/**
* calculate_imbalance - Calculate the amount of imbalance present within the
* groups of a given sched_domain during load balance.
* @env: load balance environment
* @sds: statistics of the sched_domain whose imbalance is to be calculated.
*/
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
{
struct sg_lb_stats *local, *busiest;
local = &sds->local_stat;
busiest = &sds->busiest_stat;
if (busiest->group_type == group_misfit_task) {
if (env->sd->flags & SD_ASYM_CPUCAPACITY) {
/* Set imbalance to allow misfit tasks to be balanced. */
env->migration_type = migrate_misfit;
env->imbalance = 1;
} else {
/*
* Set load imbalance to allow moving task from cpu
* with reduced capacity.
*/
env->migration_type = migrate_load;
env->imbalance = busiest->group_misfit_task_load;
}
return;
}
if (busiest->group_type == group_asym_packing) {
/*
* In case of asym capacity, we will try to migrate all load to
* the preferred CPU.
*/
env->migration_type = migrate_task;
env->imbalance = busiest->sum_h_nr_running;
return;
}
if (busiest->group_type == group_imbalanced) {
/*
* In the group_imb case we cannot rely on group-wide averages
* to ensure CPU-load equilibrium, try to move any task to fix
* the imbalance. The next load balance will take care of
* balancing back the system.
*/
env->migration_type = migrate_task;
env->imbalance = 1;
return;
}
/*
* Try to use spare capacity of local group without overloading it or
* emptying busiest.
*/
if (local->group_type == group_has_spare) {
if ((busiest->group_type > group_fully_busy) &&
!(env->sd->flags & SD_SHARE_PKG_RESOURCES)) {
/*
* If busiest is overloaded, try to fill spare
* capacity. This might end up creating spare capacity
* in busiest or busiest still being overloaded but
* there is no simple way to directly compute the
* amount of load to migrate in order to balance the
* system.
*/
env->migration_type = migrate_util;
env->imbalance = max(local->group_capacity, local->group_util) -
local->group_util;
/*
* In some cases, the group's utilization is max or even
* higher than capacity because of migrations but the
* local CPU is (newly) idle. There is at least one
* waiting task in this overloaded busiest group. Let's
* try to pull it.
*/
if (env->idle != CPU_NOT_IDLE && env->imbalance == 0) {
env->migration_type = migrate_task;
env->imbalance = 1;
}
return;
}
if (busiest->group_weight == 1 || sds->prefer_sibling) {
unsigned int nr_diff = busiest->sum_nr_running;
/*
* When prefer sibling, evenly spread running tasks on
* groups.
*/
env->migration_type = migrate_task;
lsub_positive(&nr_diff, local->sum_nr_running);
env->imbalance = nr_diff;
} else {
/*
* If there is no overload, we just want to even the number of
* idle cpus.
*/
env->migration_type = migrate_task;
env->imbalance = max_t(long, 0,
(local->idle_cpus - busiest->idle_cpus));
}
#ifdef CONFIG_NUMA
/* Consider allowing a small imbalance between NUMA groups */
if (env->sd->flags & SD_NUMA) {
env->imbalance = adjust_numa_imbalance(env->imbalance,
local->sum_nr_running + 1,
env->sd->imb_numa_nr);
}
#endif
/* Number of tasks to move to restore balance */
env->imbalance >>= 1;
return;
}
/*
* Local is fully busy but has to take more load to relieve the
* busiest group
*/
if (local->group_type < group_overloaded) {
/*
* Local will become overloaded so the avg_load metrics are
* finally needed.
*/
local->avg_load = (local->group_load * SCHED_CAPACITY_SCALE) /
local->group_capacity;
/*
* If the local group is more loaded than the selected
* busiest group don't try to pull any tasks.
*/
if (local->avg_load >= busiest->avg_load) {
env->imbalance = 0;
return;
}
sds->avg_load = (sds->total_load * SCHED_CAPACITY_SCALE) /
sds->total_capacity;
/*
* If the local group is more loaded than the average system
* load, don't try to pull any tasks.
*/
if (local->avg_load >= sds->avg_load) {
env->imbalance = 0;
return;
}
}
/*
* Both group are or will become overloaded and we're trying to get all
* the CPUs to the average_load, so we don't want to push ourselves
* above the average load, nor do we wish to reduce the max loaded CPU
* below the average load. At the same time, we also don't want to
* reduce the group load below the group capacity. Thus we look for
* the minimum possible imbalance.
*/
env->migration_type = migrate_load;
env->imbalance = min(
(busiest->avg_load - sds->avg_load) * busiest->group_capacity,
(sds->avg_load - local->avg_load) * local->group_capacity
) / SCHED_CAPACITY_SCALE;
}
/******* find_busiest_group() helpers end here *********************/
/*
* Decision matrix according to the local and busiest group type:
*
* busiest \ local has_spare fully_busy misfit asym imbalanced overloaded
* has_spare nr_idle balanced N/A N/A balanced balanced
* fully_busy nr_idle nr_idle N/A N/A balanced balanced
* misfit_task force N/A N/A N/A N/A N/A
* asym_packing force force N/A N/A force force
* imbalanced force force N/A N/A force force
* overloaded force force N/A N/A force avg_load
*
* N/A : Not Applicable because already filtered while updating
* statistics.
* balanced : The system is balanced for these 2 groups.
* force : Calculate the imbalance as load migration is probably needed.
* avg_load : Only if imbalance is significant enough.
* nr_idle : dst_cpu is not busy and the number of idle CPUs is quite
* different in groups.
*/
/**
* find_busiest_group - Returns the busiest group within the sched_domain
* if there is an imbalance.
* @env: The load balancing environment.
*
* Also calculates the amount of runnable load which should be moved
* to restore balance.
*
* Return: - The busiest group if imbalance exists.
*/
static struct sched_group *find_busiest_group(struct lb_env *env)
{
struct sg_lb_stats *local, *busiest;
struct sd_lb_stats sds;
init_sd_lb_stats(&sds);
/*
* Compute the various statistics relevant for load balancing at
* this level.
*/
update_sd_lb_stats(env, &sds);
/* There is no busy sibling group to pull tasks from */
if (!sds.busiest)
goto out_balanced;
busiest = &sds.busiest_stat;
/* Misfit tasks should be dealt with regardless of the avg load */
if (busiest->group_type == group_misfit_task)
goto force_balance;
if (sched_energy_enabled()) {
struct root_domain *rd = env->dst_rq->rd;
if (rcu_dereference(rd->pd) && !READ_ONCE(rd->overutilized))
goto out_balanced;
}
/* ASYM feature bypasses nice load balance check */
if (busiest->group_type == group_asym_packing)
goto force_balance;
/*
* If the busiest group is imbalanced the below checks don't
* work because they assume all things are equal, which typically
* isn't true due to cpus_ptr constraints and the like.
*/
if (busiest->group_type == group_imbalanced)
goto force_balance;
local = &sds.local_stat;
/*
* If the local group is busier than the selected busiest group
* don't try and pull any tasks.
*/
if (local->group_type > busiest->group_type)
goto out_balanced;
/*
* When groups are overloaded, use the avg_load to ensure fairness
* between tasks.
*/
if (local->group_type == group_overloaded) {
/*
* If the local group is more loaded than the selected
* busiest group don't try to pull any tasks.
*/
if (local->avg_load >= busiest->avg_load)
goto out_balanced;
/* XXX broken for overlapping NUMA groups */
sds.avg_load = (sds.total_load * SCHED_CAPACITY_SCALE) /
sds.total_capacity;
/*
* Don't pull any tasks if this group is already above the
* domain average load.
*/
if (local->avg_load >= sds.avg_load)
goto out_balanced;
/*
* If the busiest group is more loaded, use imbalance_pct to be
* conservative.
*/
if (100 * busiest->avg_load <=
env->sd->imbalance_pct * local->avg_load)
goto out_balanced;
}
/*
* Try to move all excess tasks to a sibling domain of the busiest
* group's child domain.
*/
if (sds.prefer_sibling && local->group_type == group_has_spare &&
busiest->sum_nr_running > local->sum_nr_running + 1)
goto force_balance;
if (busiest->group_type != group_overloaded) {
if (env->idle == CPU_NOT_IDLE)
/*
* If the busiest group is not overloaded (and as a
* result the local one too) but this CPU is already
* busy, let another idle CPU try to pull task.
*/
goto out_balanced;
if (busiest->group_weight > 1 &&
local->idle_cpus <= (busiest->idle_cpus + 1))
/*
* If the busiest group is not overloaded
* and there is no imbalance between this and busiest
* group wrt idle CPUs, it is balanced. The imbalance
* becomes significant if the diff is greater than 1
* otherwise we might end up to just move the imbalance
* on another group. Of course this applies only if
* there is more than 1 CPU per group.
*/
goto out_balanced;
if (busiest->sum_h_nr_running == 1)
/*
* busiest doesn't have any tasks waiting to run
*/
goto out_balanced;
}
force_balance:
/* Looks like there is an imbalance. Compute it */
calculate_imbalance(env, &sds);
return env->imbalance ? sds.busiest : NULL;
out_balanced:
env->imbalance = 0;
return NULL;
}
/*
* find_busiest_queue - find the busiest runqueue among the CPUs in the group.
*/
static struct rq *find_busiest_queue(struct lb_env *env,
struct sched_group *group)
{
struct rq *busiest = NULL, *rq;
unsigned long busiest_util = 0, busiest_load = 0, busiest_capacity = 1;
unsigned int busiest_nr = 0;
int i;
for_each_cpu_and(i, sched_group_span(group), env->cpus) {
unsigned long capacity, load, util;
unsigned int nr_running;
enum fbq_type rt;
rq = cpu_rq(i);
rt = fbq_classify_rq(rq);
/*
* We classify groups/runqueues into three groups:
* - regular: there are !numa tasks
* - remote: there are numa tasks that run on the 'wrong' node
* - all: there is no distinction
*
* In order to avoid migrating ideally placed numa tasks,
* ignore those when there's better options.
*
* If we ignore the actual busiest queue to migrate another
* task, the next balance pass can still reduce the busiest
* queue by moving tasks around inside the node.
*
* If we cannot move enough load due to this classification
* the next pass will adjust the group classification and
* allow migration of more tasks.
*
* Both cases only affect the total convergence complexity.
*/
if (rt > env->fbq_type)
continue;
nr_running = rq->cfs.h_nr_running;
if (!nr_running)
continue;
capacity = capacity_of(i);
/*
* For ASYM_CPUCAPACITY domains, don't pick a CPU that could
* eventually lead to active_balancing high->low capacity.
* Higher per-CPU capacity is considered better than balancing
* average load.
*/
if (env->sd->flags & SD_ASYM_CPUCAPACITY &&
!capacity_greater(capacity_of(env->dst_cpu), capacity) &&
nr_running == 1)
continue;
/*
* Make sure we only pull tasks from a CPU of lower priority
* when balancing between SMT siblings.
*
* If balancing between cores, let lower priority CPUs help
* SMT cores with more than one busy sibling.
*/
if ((env->sd->flags & SD_ASYM_PACKING) &&
sched_use_asym_prio(env->sd, i) &&
sched_asym_prefer(i, env->dst_cpu) &&
nr_running == 1)
continue;
switch (env->migration_type) {
case migrate_load:
/*
* When comparing with load imbalance, use cpu_load()
* which is not scaled with the CPU capacity.
*/
load = cpu_load(rq);
if (nr_running == 1 && load > env->imbalance &&
!check_cpu_capacity(rq, env->sd))
break;
/*
* For the load comparisons with the other CPUs,
* consider the cpu_load() scaled with the CPU
* capacity, so that the load can be moved away
* from the CPU that is potentially running at a
* lower capacity.
*
* Thus we're looking for max(load_i / capacity_i),
* crosswise multiplication to rid ourselves of the
* division works out to:
* load_i * capacity_j > load_j * capacity_i;
* where j is our previous maximum.
*/
if (load * busiest_capacity > busiest_load * capacity) {
busiest_load = load;
busiest_capacity = capacity;
busiest = rq;
}
break;
case migrate_util:
util = cpu_util_cfs_boost(i);
/*
* Don't try to pull utilization from a CPU with one
* running task. Whatever its utilization, we will fail
* detach the task.
*/
if (nr_running <= 1)
continue;
if (busiest_util < util) {
busiest_util = util;
busiest = rq;
}
break;
case migrate_task:
if (busiest_nr < nr_running) {
busiest_nr = nr_running;
busiest = rq;
}
break;
case migrate_misfit:
/*
* For ASYM_CPUCAPACITY domains with misfit tasks we
* simply seek the "biggest" misfit task.
*/
if (rq->misfit_task_load > busiest_load) {
busiest_load = rq->misfit_task_load;
busiest = rq;
}
break;
}
}
return busiest;
}
/*
* Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
* so long as it is large enough.
*/
#define MAX_PINNED_INTERVAL 512
static inline bool
asym_active_balance(struct lb_env *env)
{
/*
* ASYM_PACKING needs to force migrate tasks from busy but lower
* priority CPUs in order to pack all tasks in the highest priority
* CPUs. When done between cores, do it only if the whole core if the
* whole core is idle.
*
* If @env::src_cpu is an SMT core with busy siblings, let
* the lower priority @env::dst_cpu help it. Do not follow
* CPU priority.
*/
return env->idle != CPU_NOT_IDLE && (env->sd->flags & SD_ASYM_PACKING) &&
sched_use_asym_prio(env->sd, env->dst_cpu) &&
(sched_asym_prefer(env->dst_cpu, env->src_cpu) ||
!sched_use_asym_prio(env->sd, env->src_cpu));
}
static inline bool
imbalanced_active_balance(struct lb_env *env)
{
struct sched_domain *sd = env->sd;
/*
* The imbalanced case includes the case of pinned tasks preventing a fair
* distribution of the load on the system but also the even distribution of the
* threads on a system with spare capacity
*/
if ((env->migration_type == migrate_task) &&
(sd->nr_balance_failed > sd->cache_nice_tries+2))
return 1;
return 0;
}
static int need_active_balance(struct lb_env *env)
{
struct sched_domain *sd = env->sd;
if (asym_active_balance(env))
return 1;
if (imbalanced_active_balance(env))
return 1;
/*
* The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
* It's worth migrating the task if the src_cpu's capacity is reduced
* because of other sched_class or IRQs if more capacity stays
* available on dst_cpu.
*/
if ((env->idle != CPU_NOT_IDLE) &&
(env->src_rq->cfs.h_nr_running == 1)) {
if ((check_cpu_capacity(env->src_rq, sd)) &&
(capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
return 1;
}
if (env->migration_type == migrate_misfit)
return 1;
return 0;
}
static int active_load_balance_cpu_stop(void *data);
static int should_we_balance(struct lb_env *env)
{
struct sched_group *sg = env->sd->groups;
int cpu;
/*
* Ensure the balancing environment is consistent; can happen
* when the softirq triggers 'during' hotplug.
*/
if (!cpumask_test_cpu(env->dst_cpu, env->cpus))
return 0;
/*
* In the newly idle case, we will allow all the CPUs
* to do the newly idle load balance.
*
* However, we bail out if we already have tasks or a wakeup pending,
* to optimize wakeup latency.
*/
if (env->idle == CPU_NEWLY_IDLE) {
if (env->dst_rq->nr_running > 0 || env->dst_rq->ttwu_pending)
return 0;
return 1;
}
/* Try to find first idle CPU */
for_each_cpu_and(cpu, group_balance_mask(sg), env->cpus) {
if (!idle_cpu(cpu))
continue;
/* Are we the first idle CPU? */
return cpu == env->dst_cpu;
}
/* Are we the first CPU of this group ? */
return group_balance_cpu(sg) == env->dst_cpu;
}
/*
* Check this_cpu to ensure it is balanced within domain. Attempt to move
* tasks if there is an imbalance.
*/
static int load_balance(int this_cpu, struct rq *this_rq,
struct sched_domain *sd, enum cpu_idle_type idle,
int *continue_balancing)
{
int ld_moved, cur_ld_moved, active_balance = 0;
struct sched_domain *sd_parent = sd->parent;
struct sched_group *group;
struct rq *busiest;
struct rq_flags rf;
struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
struct lb_env env = {
.sd = sd,
.dst_cpu = this_cpu,
.dst_rq = this_rq,
.dst_grpmask = group_balance_mask(sd->groups),
.idle = idle,
.loop_break = SCHED_NR_MIGRATE_BREAK,
.cpus = cpus,
.fbq_type = all,
.tasks = LIST_HEAD_INIT(env.tasks),
};
cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);
schedstat_inc(sd->lb_count[idle]);
redo:
if (!should_we_balance(&env)) {
*continue_balancing = 0;
goto out_balanced;
}
group = find_busiest_group(&env);
if (!group) {
schedstat_inc(sd->lb_nobusyg[idle]);
goto out_balanced;
}
busiest = find_busiest_queue(&env, group);
if (!busiest) {
schedstat_inc(sd->lb_nobusyq[idle]);
goto out_balanced;
}
WARN_ON_ONCE(busiest == env.dst_rq);
schedstat_add(sd->lb_imbalance[idle], env.imbalance);
env.src_cpu = busiest->cpu;
env.src_rq = busiest;
ld_moved = 0;
/* Clear this flag as soon as we find a pullable task */
env.flags |= LBF_ALL_PINNED;
if (busiest->nr_running > 1) {
/*
* Attempt to move tasks. If find_busiest_group has found
* an imbalance but busiest->nr_running <= 1, the group is
* still unbalanced. ld_moved simply stays zero, so it is
* correctly treated as an imbalance.
*/
env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
more_balance:
rq_lock_irqsave(busiest, &rf);
update_rq_clock(busiest);
/*
* cur_ld_moved - load moved in current iteration
* ld_moved - cumulative load moved across iterations
*/
cur_ld_moved = detach_tasks(&env);
/*
* We've detached some tasks from busiest_rq. Every
* task is masked "TASK_ON_RQ_MIGRATING", so we can safely
* unlock busiest->lock, and we are able to be sure
* that nobody can manipulate the tasks in parallel.
* See task_rq_lock() family for the details.
*/
rq_unlock(busiest, &rf);
if (cur_ld_moved) {
attach_tasks(&env);
ld_moved += cur_ld_moved;
}
local_irq_restore(rf.flags);
if (env.flags & LBF_NEED_BREAK) {
env.flags &= ~LBF_NEED_BREAK;
/* Stop if we tried all running tasks */
if (env.loop < busiest->nr_running)
goto more_balance;
}
/*
* Revisit (affine) tasks on src_cpu that couldn't be moved to
* us and move them to an alternate dst_cpu in our sched_group
* where they can run. The upper limit on how many times we
* iterate on same src_cpu is dependent on number of CPUs in our
* sched_group.
*
* This changes load balance semantics a bit on who can move
* load to a given_cpu. In addition to the given_cpu itself
* (or a ilb_cpu acting on its behalf where given_cpu is
* nohz-idle), we now have balance_cpu in a position to move
* load to given_cpu. In rare situations, this may cause
* conflicts (balance_cpu and given_cpu/ilb_cpu deciding
* _independently_ and at _same_ time to move some load to
* given_cpu) causing excess load to be moved to given_cpu.
* This however should not happen so much in practice and
* moreover subsequent load balance cycles should correct the
* excess load moved.
*/
if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
/* Prevent to re-select dst_cpu via env's CPUs */
__cpumask_clear_cpu(env.dst_cpu, env.cpus);
env.dst_rq = cpu_rq(env.new_dst_cpu);
env.dst_cpu = env.new_dst_cpu;
env.flags &= ~LBF_DST_PINNED;
env.loop = 0;
env.loop_break = SCHED_NR_MIGRATE_BREAK;
/*
* Go back to "more_balance" rather than "redo" since we
* need to continue with same src_cpu.
*/
goto more_balance;
}
/*
* We failed to reach balance because of affinity.
*/
if (sd_parent) {
int *group_imbalance = &sd_parent->groups->sgc->imbalance;
if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
*group_imbalance = 1;
}
/* All tasks on this runqueue were pinned by CPU affinity */
if (unlikely(env.flags & LBF_ALL_PINNED)) {
__cpumask_clear_cpu(cpu_of(busiest), cpus);
/*
* Attempting to continue load balancing at the current
* sched_domain level only makes sense if there are
* active CPUs remaining as possible busiest CPUs to
* pull load from which are not contained within the
* destination group that is receiving any migrated
* load.
*/
if (!cpumask_subset(cpus, env.dst_grpmask)) {
env.loop = 0;
env.loop_break = SCHED_NR_MIGRATE_BREAK;
goto redo;
}
goto out_all_pinned;
}
}
if (!ld_moved) {
schedstat_inc(sd->lb_failed[idle]);
/*
* Increment the failure counter only on periodic balance.
* We do not want newidle balance, which can be very
* frequent, pollute the failure counter causing
* excessive cache_hot migrations and active balances.
*/
if (idle != CPU_NEWLY_IDLE)
sd->nr_balance_failed++;
if (need_active_balance(&env)) {
unsigned long flags;
raw_spin_rq_lock_irqsave(busiest, flags);
/*
* Don't kick the active_load_balance_cpu_stop,
* if the curr task on busiest CPU can't be
* moved to this_cpu:
*/
if (!cpumask_test_cpu(this_cpu, busiest->curr->cpus_ptr)) {
raw_spin_rq_unlock_irqrestore(busiest, flags);
goto out_one_pinned;
}
/* Record that we found at least one task that could run on this_cpu */
env.flags &= ~LBF_ALL_PINNED;
/*
* ->active_balance synchronizes accesses to
* ->active_balance_work. Once set, it's cleared
* only after active load balance is finished.
*/
if (!busiest->active_balance) {
busiest->active_balance = 1;
busiest->push_cpu = this_cpu;
active_balance = 1;
}
raw_spin_rq_unlock_irqrestore(busiest, flags);
if (active_balance) {
stop_one_cpu_nowait(cpu_of(busiest),
active_load_balance_cpu_stop, busiest,
&busiest->active_balance_work);
}
}
} else {
sd->nr_balance_failed = 0;
}
if (likely(!active_balance) || need_active_balance(&env)) {
/* We were unbalanced, so reset the balancing interval */
sd->balance_interval = sd->min_interval;
}
goto out;
out_balanced:
/*
* We reach balance although we may have faced some affinity
* constraints. Clear the imbalance flag only if other tasks got
* a chance to move and fix the imbalance.
*/
if (sd_parent && !(env.flags & LBF_ALL_PINNED)) {
int *group_imbalance = &sd_parent->groups->sgc->imbalance;
if (*group_imbalance)
*group_imbalance = 0;
}
out_all_pinned:
/*
* We reach balance because all tasks are pinned at this level so
* we can't migrate them. Let the imbalance flag set so parent level
* can try to migrate them.
*/
schedstat_inc(sd->lb_balanced[idle]);
sd->nr_balance_failed = 0;
out_one_pinned:
ld_moved = 0;
/*
* newidle_balance() disregards balance intervals, so we could
* repeatedly reach this code, which would lead to balance_interval
* skyrocketing in a short amount of time. Skip the balance_interval
* increase logic to avoid that.
*/
if (env.idle == CPU_NEWLY_IDLE)
goto out;
/* tune up the balancing interval */
if ((env.flags & LBF_ALL_PINNED &&
sd->balance_interval < MAX_PINNED_INTERVAL) ||
sd->balance_interval < sd->max_interval)
sd->balance_interval *= 2;
out:
return ld_moved;
}
static inline unsigned long
get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
{
unsigned long interval = sd->balance_interval;
if (cpu_busy)
interval *= sd->busy_factor;
/* scale ms to jiffies */
interval = msecs_to_jiffies(interval);
/*
* Reduce likelihood of busy balancing at higher domains racing with
* balancing at lower domains by preventing their balancing periods
* from being multiples of each other.
*/
if (cpu_busy)
interval -= 1;
interval = clamp(interval, 1UL, max_load_balance_interval);
return interval;
}
static inline void
update_next_balance(struct sched_domain *sd, unsigned long *next_balance)
{
unsigned long interval, next;
/* used by idle balance, so cpu_busy = 0 */
interval = get_sd_balance_interval(sd, 0);
next = sd->last_balance + interval;
if (time_after(*next_balance, next))
*next_balance = next;
}
/*
* active_load_balance_cpu_stop is run by the CPU stopper. It pushes
* running tasks off the busiest CPU onto idle CPUs. It requires at
* least 1 task to be running on each physical CPU where possible, and
* avoids physical / logical imbalances.
*/
static int active_load_balance_cpu_stop(void *data)
{
struct rq *busiest_rq = data;
int busiest_cpu = cpu_of(busiest_rq);
int target_cpu = busiest_rq->push_cpu;
struct rq *target_rq = cpu_rq(target_cpu);
struct sched_domain *sd;
struct task_struct *p = NULL;
struct rq_flags rf;
rq_lock_irq(busiest_rq, &rf);
/*
* Between queueing the stop-work and running it is a hole in which
* CPUs can become inactive. We should not move tasks from or to
* inactive CPUs.
*/
if (!cpu_active(busiest_cpu) || !cpu_active(target_cpu))
goto out_unlock;
/* Make sure the requested CPU hasn't gone down in the meantime: */
if (unlikely(busiest_cpu != smp_processor_id() ||
!busiest_rq->active_balance))
goto out_unlock;
/* Is there any task to move? */
if (busiest_rq->nr_running <= 1)
goto out_unlock;
/*
* This condition is "impossible", if it occurs
* we need to fix it. Originally reported by
* Bjorn Helgaas on a 128-CPU setup.
*/
WARN_ON_ONCE(busiest_rq == target_rq);
/* Search for an sd spanning us and the target CPU. */
rcu_read_lock();
for_each_domain(target_cpu, sd) {
if (cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
break;
}
if (likely(sd)) {
struct lb_env env = {
.sd = sd,
.dst_cpu = target_cpu,
.dst_rq = target_rq,
.src_cpu = busiest_rq->cpu,
.src_rq = busiest_rq,
.idle = CPU_IDLE,
.flags = LBF_ACTIVE_LB,
};
schedstat_inc(sd->alb_count);
update_rq_clock(busiest_rq);
p = detach_one_task(&env);
if (p) {
schedstat_inc(sd->alb_pushed);
/* Active balancing done, reset the failure counter. */
sd->nr_balance_failed = 0;
} else {
schedstat_inc(sd->alb_failed);
}
}
rcu_read_unlock();
out_unlock:
busiest_rq->active_balance = 0;
rq_unlock(busiest_rq, &rf);
if (p)
attach_one_task(target_rq, p);
local_irq_enable();
return 0;
}
static DEFINE_SPINLOCK(balancing);
/*
* Scale the max load_balance interval with the number of CPUs in the system.
* This trades load-balance latency on larger machines for less cross talk.
*/
void update_max_interval(void)
{
max_load_balance_interval = HZ*num_online_cpus()/10;
}
static inline bool update_newidle_cost(struct sched_domain *sd, u64 cost)
{
if (cost > sd->max_newidle_lb_cost) {
/*
* Track max cost of a domain to make sure to not delay the
* next wakeup on the CPU.
*/
sd->max_newidle_lb_cost = cost;
sd->last_decay_max_lb_cost = jiffies;
} else if (time_after(jiffies, sd->last_decay_max_lb_cost + HZ)) {
/*
* Decay the newidle max times by ~1% per second to ensure that
* it is not outdated and the current max cost is actually
* shorter.
*/
sd->max_newidle_lb_cost = (sd->max_newidle_lb_cost * 253) / 256;
sd->last_decay_max_lb_cost = jiffies;
return true;
}
return false;
}
/*
* It checks each scheduling domain to see if it is due to be balanced,
* and initiates a balancing operation if so.
*
* Balancing parameters are set up in init_sched_domains.
*/
static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
{
int continue_balancing = 1;
int cpu = rq->cpu;
int busy = idle != CPU_IDLE && !sched_idle_cpu(cpu);
unsigned long interval;
struct sched_domain *sd;
/* Earliest time when we have to do rebalance again */
unsigned long next_balance = jiffies + 60*HZ;
int update_next_balance = 0;
int need_serialize, need_decay = 0;
u64 max_cost = 0;
rcu_read_lock();
for_each_domain(cpu, sd) {
/*
* Decay the newidle max times here because this is a regular
* visit to all the domains.
*/
need_decay = update_newidle_cost(sd, 0);
max_cost += sd->max_newidle_lb_cost;
/*
* Stop the load balance at this level. There is another
* CPU in our sched group which is doing load balancing more
* actively.
*/
if (!continue_balancing) {
if (need_decay)
continue;
break;
}
interval = get_sd_balance_interval(sd, busy);
need_serialize = sd->flags & SD_SERIALIZE;
if (need_serialize) {
if (!spin_trylock(&balancing))
goto out;
}
if (time_after_eq(jiffies, sd->last_balance + interval)) {
if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
/*
* The LBF_DST_PINNED logic could have changed
* env->dst_cpu, so we can't know our idle
* state even if we migrated tasks. Update it.
*/
idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
busy = idle != CPU_IDLE && !sched_idle_cpu(cpu);
}
sd->last_balance = jiffies;
interval = get_sd_balance_interval(sd, busy);
}
if (need_serialize)
spin_unlock(&balancing);
out:
if (time_after(next_balance, sd->last_balance + interval)) {
next_balance = sd->last_balance + interval;
update_next_balance = 1;
}
}
if (need_decay) {
/*
* Ensure the rq-wide value also decays but keep it at a
* reasonable floor to avoid funnies with rq->avg_idle.
*/
rq->max_idle_balance_cost =
max((u64)sysctl_sched_migration_cost, max_cost);
}
rcu_read_unlock();
/*
* next_balance will be updated only when there is a need.
* When the cpu is attached to null domain for ex, it will not be
* updated.
*/
if (likely(update_next_balance))
rq->next_balance = next_balance;
}
static inline int on_null_domain(struct rq *rq)
{
return unlikely(!rcu_dereference_sched(rq->sd));
}
#ifdef CONFIG_NO_HZ_COMMON
/*
* idle load balancing details
* - When one of the busy CPUs notice that there may be an idle rebalancing
* needed, they will kick the idle load balancer, which then does idle
* load balancing for all the idle CPUs.
* - HK_TYPE_MISC CPUs are used for this task, because HK_TYPE_SCHED not set
* anywhere yet.
*/
static inline int find_new_ilb(void)
{
int ilb;
const struct cpumask *hk_mask;
hk_mask = housekeeping_cpumask(HK_TYPE_MISC);
for_each_cpu_and(ilb, nohz.idle_cpus_mask, hk_mask) {
if (ilb == smp_processor_id())
continue;
if (idle_cpu(ilb))
return ilb;
}
return nr_cpu_ids;
}
/*
* Kick a CPU to do the nohz balancing, if it is time for it. We pick any
* idle CPU in the HK_TYPE_MISC housekeeping set (if there is one).
*/
static void kick_ilb(unsigned int flags)
{
int ilb_cpu;
/*
* Increase nohz.next_balance only when if full ilb is triggered but
* not if we only update stats.
*/
if (flags & NOHZ_BALANCE_KICK)
nohz.next_balance = jiffies+1;
ilb_cpu = find_new_ilb();
if (ilb_cpu >= nr_cpu_ids)
return;
/*
* Access to rq::nohz_csd is serialized by NOHZ_KICK_MASK; he who sets
* the first flag owns it; cleared by nohz_csd_func().
*/
flags = atomic_fetch_or(flags, nohz_flags(ilb_cpu));
if (flags & NOHZ_KICK_MASK)
return;
/*
* This way we generate an IPI on the target CPU which
* is idle. And the softirq performing nohz idle load balance
* will be run before returning from the IPI.
*/
smp_call_function_single_async(ilb_cpu, &cpu_rq(ilb_cpu)->nohz_csd);
}
/*
* Current decision point for kicking the idle load balancer in the presence
* of idle CPUs in the system.
*/
static void nohz_balancer_kick(struct rq *rq)
{
unsigned long now = jiffies;
struct sched_domain_shared *sds;
struct sched_domain *sd;
int nr_busy, i, cpu = rq->cpu;
unsigned int flags = 0;
if (unlikely(rq->idle_balance))
return;
/*
* We may be recently in ticked or tickless idle mode. At the first
* busy tick after returning from idle, we will update the busy stats.
*/
nohz_balance_exit_idle(rq);
/*
* None are in tickless mode and hence no need for NOHZ idle load
* balancing.
*/
if (likely(!atomic_read(&nohz.nr_cpus)))
return;
if (READ_ONCE(nohz.has_blocked) &&
time_after(now, READ_ONCE(nohz.next_blocked)))
flags = NOHZ_STATS_KICK;
if (time_before(now, nohz.next_balance))
goto out;
if (rq->nr_running >= 2) {
flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
goto out;
}
rcu_read_lock();
sd = rcu_dereference(rq->sd);
if (sd) {
/*
* If there's a CFS task and the current CPU has reduced
* capacity; kick the ILB to see if there's a better CPU to run
* on.
*/
if (rq->cfs.h_nr_running >= 1 && check_cpu_capacity(rq, sd)) {
flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
goto unlock;
}
}
sd = rcu_dereference(per_cpu(sd_asym_packing, cpu));
if (sd) {
/*
* When ASYM_PACKING; see if there's a more preferred CPU
* currently idle; in which case, kick the ILB to move tasks
* around.
*
* When balancing betwen cores, all the SMT siblings of the
* preferred CPU must be idle.
*/
for_each_cpu_and(i, sched_domain_span(sd), nohz.idle_cpus_mask) {
if (sched_use_asym_prio(sd, i) &&
sched_asym_prefer(i, cpu)) {
flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
goto unlock;
}
}
}
sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, cpu));
if (sd) {
/*
* When ASYM_CPUCAPACITY; see if there's a higher capacity CPU
* to run the misfit task on.
*/
if (check_misfit_status(rq, sd)) {
flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
goto unlock;
}
/*
* For asymmetric systems, we do not want to nicely balance
* cache use, instead we want to embrace asymmetry and only
* ensure tasks have enough CPU capacity.
*
* Skip the LLC logic because it's not relevant in that case.
*/
goto unlock;
}
sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
if (sds) {
/*
* If there is an imbalance between LLC domains (IOW we could
* increase the overall cache use), we need some less-loaded LLC
* domain to pull some load. Likewise, we may need to spread
* load within the current LLC domain (e.g. packed SMT cores but
* other CPUs are idle). We can't really know from here how busy
* the others are - so just get a nohz balance going if it looks
* like this LLC domain has tasks we could move.
*/
nr_busy = atomic_read(&sds->nr_busy_cpus);
if (nr_busy > 1) {
flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
goto unlock;
}
}
unlock:
rcu_read_unlock();
out:
if (READ_ONCE(nohz.needs_update))
flags |= NOHZ_NEXT_KICK;
if (flags)
kick_ilb(flags);
}
static void set_cpu_sd_state_busy(int cpu)
{
struct sched_domain *sd;
rcu_read_lock();
sd = rcu_dereference(per_cpu(sd_llc, cpu));
if (!sd || !sd->nohz_idle)
goto unlock;
sd->nohz_idle = 0;
atomic_inc(&sd->shared->nr_busy_cpus);
unlock:
rcu_read_unlock();
}
void nohz_balance_exit_idle(struct rq *rq)
{
SCHED_WARN_ON(rq != this_rq());
if (likely(!rq->nohz_tick_stopped))
return;
rq->nohz_tick_stopped = 0;
cpumask_clear_cpu(rq->cpu, nohz.idle_cpus_mask);
atomic_dec(&nohz.nr_cpus);
set_cpu_sd_state_busy(rq->cpu);
}
static void set_cpu_sd_state_idle(int cpu)
{
struct sched_domain *sd;
rcu_read_lock();
sd = rcu_dereference(per_cpu(sd_llc, cpu));
if (!sd || sd->nohz_idle)
goto unlock;
sd->nohz_idle = 1;
atomic_dec(&sd->shared->nr_busy_cpus);
unlock:
rcu_read_unlock();
}
/*
* This routine will record that the CPU is going idle with tick stopped.
* This info will be used in performing idle load balancing in the future.
*/
void nohz_balance_enter_idle(int cpu)
{
struct rq *rq = cpu_rq(cpu);
SCHED_WARN_ON(cpu != smp_processor_id());
/* If this CPU is going down, then nothing needs to be done: */
if (!cpu_active(cpu))
return;
/* Spare idle load balancing on CPUs that don't want to be disturbed: */
if (!housekeeping_cpu(cpu, HK_TYPE_SCHED))
return;
/*
* Can be set safely without rq->lock held
* If a clear happens, it will have evaluated last additions because
* rq->lock is held during the check and the clear
*/
rq->has_blocked_load = 1;
/*
* The tick is still stopped but load could have been added in the
* meantime. We set the nohz.has_blocked flag to trig a check of the
* *_avg. The CPU is already part of nohz.idle_cpus_mask so the clear
* of nohz.has_blocked can only happen after checking the new load
*/
if (rq->nohz_tick_stopped)
goto out;
/* If we're a completely isolated CPU, we don't play: */
if (on_null_domain(rq))
return;
rq->nohz_tick_stopped = 1;
cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
atomic_inc(&nohz.nr_cpus);
/*
* Ensures that if nohz_idle_balance() fails to observe our
* @idle_cpus_mask store, it must observe the @has_blocked
* and @needs_update stores.
*/
smp_mb__after_atomic();
set_cpu_sd_state_idle(cpu);
WRITE_ONCE(nohz.needs_update, 1);
out:
/*
* Each time a cpu enter idle, we assume that it has blocked load and
* enable the periodic update of the load of idle cpus
*/
WRITE_ONCE(nohz.has_blocked, 1);
}
static bool update_nohz_stats(struct rq *rq)
{
unsigned int cpu = rq->cpu;
if (!rq->has_blocked_load)
return false;
if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
return false;
if (!time_after(jiffies, READ_ONCE(rq->last_blocked_load_update_tick)))
return true;
update_blocked_averages(cpu);
return rq->has_blocked_load;
}
/*
* Internal function that runs load balance for all idle cpus. The load balance
* can be a simple update of blocked load or a complete load balance with
* tasks movement depending of flags.
*/
static void _nohz_idle_balance(struct rq *this_rq, unsigned int flags)
{
/* Earliest time when we have to do rebalance again */
unsigned long now = jiffies;
unsigned long next_balance = now + 60*HZ;
bool has_blocked_load = false;
int update_next_balance = 0;
int this_cpu = this_rq->cpu;
int balance_cpu;
struct rq *rq;
SCHED_WARN_ON((flags & NOHZ_KICK_MASK) == NOHZ_BALANCE_KICK);
/*
* We assume there will be no idle load after this update and clear
* the has_blocked flag. If a cpu enters idle in the mean time, it will
* set the has_blocked flag and trigger another update of idle load.
* Because a cpu that becomes idle, is added to idle_cpus_mask before
* setting the flag, we are sure to not clear the state and not
* check the load of an idle cpu.
*
* Same applies to idle_cpus_mask vs needs_update.
*/
if (flags & NOHZ_STATS_KICK)
WRITE_ONCE(nohz.has_blocked, 0);
if (flags & NOHZ_NEXT_KICK)
WRITE_ONCE(nohz.needs_update, 0);
/*
* Ensures that if we miss the CPU, we must see the has_blocked
* store from nohz_balance_enter_idle().
*/
smp_mb();
/*
* Start with the next CPU after this_cpu so we will end with this_cpu and let a
* chance for other idle cpu to pull load.
*/
for_each_cpu_wrap(balance_cpu, nohz.idle_cpus_mask, this_cpu+1) {
if (!idle_cpu(balance_cpu))
continue;
/*
* If this CPU gets work to do, stop the load balancing
* work being done for other CPUs. Next load
* balancing owner will pick it up.
*/
if (need_resched()) {
if (flags & NOHZ_STATS_KICK)
has_blocked_load = true;
if (flags & NOHZ_NEXT_KICK)
WRITE_ONCE(nohz.needs_update, 1);
goto abort;
}
rq = cpu_rq(balance_cpu);
if (flags & NOHZ_STATS_KICK)
has_blocked_load |= update_nohz_stats(rq);
/*
* If time for next balance is due,
* do the balance.
*/
if (time_after_eq(jiffies, rq->next_balance)) {
struct rq_flags rf;
rq_lock_irqsave(rq, &rf);
update_rq_clock(rq);
rq_unlock_irqrestore(rq, &rf);
if (flags & NOHZ_BALANCE_KICK)
rebalance_domains(rq, CPU_IDLE);
}
if (time_after(next_balance, rq->next_balance)) {
next_balance = rq->next_balance;
update_next_balance = 1;
}
}
/*
* next_balance will be updated only when there is a need.
* When the CPU is attached to null domain for ex, it will not be
* updated.
*/
if (likely(update_next_balance))
nohz.next_balance = next_balance;
if (flags & NOHZ_STATS_KICK)
WRITE_ONCE(nohz.next_blocked,
now + msecs_to_jiffies(LOAD_AVG_PERIOD));
abort:
/* There is still blocked load, enable periodic update */
if (has_blocked_load)
WRITE_ONCE(nohz.has_blocked, 1);
}
/*
* In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
* rebalancing for all the cpus for whom scheduler ticks are stopped.
*/
static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
{
unsigned int flags = this_rq->nohz_idle_balance;
if (!flags)
return false;
this_rq->nohz_idle_balance = 0;
if (idle != CPU_IDLE)
return false;
_nohz_idle_balance(this_rq, flags);
return true;
}
/*
* Check if we need to run the ILB for updating blocked load before entering
* idle state.
*/
void nohz_run_idle_balance(int cpu)
{
unsigned int flags;
flags = atomic_fetch_andnot(NOHZ_NEWILB_KICK, nohz_flags(cpu));
/*
* Update the blocked load only if no SCHED_SOFTIRQ is about to happen
* (ie NOHZ_STATS_KICK set) and will do the same.
*/
if ((flags == NOHZ_NEWILB_KICK) && !need_resched())
_nohz_idle_balance(cpu_rq(cpu), NOHZ_STATS_KICK);
}
static void nohz_newidle_balance(struct rq *this_rq)
{
int this_cpu = this_rq->cpu;
/*
* This CPU doesn't want to be disturbed by scheduler
* housekeeping
*/
if (!housekeeping_cpu(this_cpu, HK_TYPE_SCHED))
return;
/* Will wake up very soon. No time for doing anything else*/
if (this_rq->avg_idle < sysctl_sched_migration_cost)
return;
/* Don't need to update blocked load of idle CPUs*/
if (!READ_ONCE(nohz.has_blocked) ||
time_before(jiffies, READ_ONCE(nohz.next_blocked)))
return;
/*
* Set the need to trigger ILB in order to update blocked load
* before entering idle state.
*/
atomic_or(NOHZ_NEWILB_KICK, nohz_flags(this_cpu));
}
#else /* !CONFIG_NO_HZ_COMMON */
static inline void nohz_balancer_kick(struct rq *rq) { }
static inline bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
{
return false;
}
static inline void nohz_newidle_balance(struct rq *this_rq) { }
#endif /* CONFIG_NO_HZ_COMMON */
/*
* newidle_balance is called by schedule() if this_cpu is about to become
* idle. Attempts to pull tasks from other CPUs.
*
* Returns:
* < 0 - we released the lock and there are !fair tasks present
* 0 - failed, no new tasks
* > 0 - success, new (fair) tasks present
*/
static int newidle_balance(struct rq *this_rq, struct rq_flags *rf)
{
unsigned long next_balance = jiffies + HZ;
int this_cpu = this_rq->cpu;
u64 t0, t1, curr_cost = 0;
struct sched_domain *sd;
int pulled_task = 0;
update_misfit_status(NULL, this_rq);
/*
* There is a task waiting to run. No need to search for one.
* Return 0; the task will be enqueued when switching to idle.
*/
if (this_rq->ttwu_pending)
return 0;
/*
* We must set idle_stamp _before_ calling idle_balance(), such that we
* measure the duration of idle_balance() as idle time.
*/
this_rq->idle_stamp = rq_clock(this_rq);
/*
* Do not pull tasks towards !active CPUs...
*/
if (!cpu_active(this_cpu))
return 0;
/*
* This is OK, because current is on_cpu, which avoids it being picked
* for load-balance and preemption/IRQs are still disabled avoiding
* further scheduler activity on it and we're being very careful to
* re-start the picking loop.
*/
rq_unpin_lock(this_rq, rf);
rcu_read_lock();
sd = rcu_dereference_check_sched_domain(this_rq->sd);
if (!READ_ONCE(this_rq->rd->overload) ||
(sd && this_rq->avg_idle < sd->max_newidle_lb_cost)) {
if (sd)
update_next_balance(sd, &next_balance);
rcu_read_unlock();
goto out;
}
rcu_read_unlock();
raw_spin_rq_unlock(this_rq);
t0 = sched_clock_cpu(this_cpu);
update_blocked_averages(this_cpu);
rcu_read_lock();
for_each_domain(this_cpu, sd) {
int continue_balancing = 1;
u64 domain_cost;
update_next_balance(sd, &next_balance);
if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost)
break;
if (sd->flags & SD_BALANCE_NEWIDLE) {
pulled_task = load_balance(this_cpu, this_rq,
sd, CPU_NEWLY_IDLE,
&continue_balancing);
t1 = sched_clock_cpu(this_cpu);
domain_cost = t1 - t0;
update_newidle_cost(sd, domain_cost);
curr_cost += domain_cost;
t0 = t1;
}
/*
* Stop searching for tasks to pull if there are
* now runnable tasks on this rq.
*/
if (pulled_task || this_rq->nr_running > 0 ||
this_rq->ttwu_pending)
break;
}
rcu_read_unlock();
raw_spin_rq_lock(this_rq);
if (curr_cost > this_rq->max_idle_balance_cost)
this_rq->max_idle_balance_cost = curr_cost;
/*
* While browsing the domains, we released the rq lock, a task could
* have been enqueued in the meantime. Since we're not going idle,
* pretend we pulled a task.
*/
if (this_rq->cfs.h_nr_running && !pulled_task)
pulled_task = 1;
/* Is there a task of a high priority class? */
if (this_rq->nr_running != this_rq->cfs.h_nr_running)
pulled_task = -1;
out:
/* Move the next balance forward */
if (time_after(this_rq->next_balance, next_balance))
this_rq->next_balance = next_balance;
if (pulled_task)
this_rq->idle_stamp = 0;
else
nohz_newidle_balance(this_rq);
rq_repin_lock(this_rq, rf);
return pulled_task;
}
/*
* run_rebalance_domains is triggered when needed from the scheduler tick.
* Also triggered for nohz idle balancing (with nohz_balancing_kick set).
*/
static __latent_entropy void run_rebalance_domains(struct softirq_action *h)
{
struct rq *this_rq = this_rq();
enum cpu_idle_type idle = this_rq->idle_balance ?
CPU_IDLE : CPU_NOT_IDLE;
/*
* If this CPU has a pending nohz_balance_kick, then do the
* balancing on behalf of the other idle CPUs whose ticks are
* stopped. Do nohz_idle_balance *before* rebalance_domains to
* give the idle CPUs a chance to load balance. Else we may
* load balance only within the local sched_domain hierarchy
* and abort nohz_idle_balance altogether if we pull some load.
*/
if (nohz_idle_balance(this_rq, idle))
return;
/* normal load balance */
update_blocked_averages(this_rq->cpu);
rebalance_domains(this_rq, idle);
}
/*
* Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
*/
void trigger_load_balance(struct rq *rq)
{
/*
* Don't need to rebalance while attached to NULL domain or
* runqueue CPU is not active
*/
if (unlikely(on_null_domain(rq) || !cpu_active(cpu_of(rq))))
return;
if (time_after_eq(jiffies, rq->next_balance))
raise_softirq(SCHED_SOFTIRQ);
nohz_balancer_kick(rq);
}
static void rq_online_fair(struct rq *rq)
{
update_sysctl();
update_runtime_enabled(rq);
}
static void rq_offline_fair(struct rq *rq)
{
update_sysctl();
/* Ensure any throttled groups are reachable by pick_next_task */
unthrottle_offline_cfs_rqs(rq);
}
#endif /* CONFIG_SMP */
#ifdef CONFIG_SCHED_CORE
static inline bool
__entity_slice_used(struct sched_entity *se, int min_nr_tasks)
{
u64 slice = sched_slice(cfs_rq_of(se), se);
u64 rtime = se->sum_exec_runtime - se->prev_sum_exec_runtime;
return (rtime * min_nr_tasks > slice);
}
#define MIN_NR_TASKS_DURING_FORCEIDLE 2
static inline void task_tick_core(struct rq *rq, struct task_struct *curr)
{
if (!sched_core_enabled(rq))
return;
/*
* If runqueue has only one task which used up its slice and
* if the sibling is forced idle, then trigger schedule to
* give forced idle task a chance.
*
* sched_slice() considers only this active rq and it gets the
* whole slice. But during force idle, we have siblings acting
* like a single runqueue and hence we need to consider runnable
* tasks on this CPU and the forced idle CPU. Ideally, we should
* go through the forced idle rq, but that would be a perf hit.
* We can assume that the forced idle CPU has at least
* MIN_NR_TASKS_DURING_FORCEIDLE - 1 tasks and use that to check
* if we need to give up the CPU.
*/
if (rq->core->core_forceidle_count && rq->cfs.nr_running == 1 &&
__entity_slice_used(&curr->se, MIN_NR_TASKS_DURING_FORCEIDLE))
resched_curr(rq);
}
/*
* se_fi_update - Update the cfs_rq->min_vruntime_fi in a CFS hierarchy if needed.
*/
static void se_fi_update(const struct sched_entity *se, unsigned int fi_seq,
bool forceidle)
{
for_each_sched_entity(se) {
struct cfs_rq *cfs_rq = cfs_rq_of(se);
if (forceidle) {
if (cfs_rq->forceidle_seq == fi_seq)
break;
cfs_rq->forceidle_seq = fi_seq;
}
cfs_rq->min_vruntime_fi = cfs_rq->min_vruntime;
}
}
void task_vruntime_update(struct rq *rq, struct task_struct *p, bool in_fi)
{
struct sched_entity *se = &p->se;
if (p->sched_class != &fair_sched_class)
return;
se_fi_update(se, rq->core->core_forceidle_seq, in_fi);
}
bool cfs_prio_less(const struct task_struct *a, const struct task_struct *b,
bool in_fi)
{
struct rq *rq = task_rq(a);
const struct sched_entity *sea = &a->se;
const struct sched_entity *seb = &b->se;
struct cfs_rq *cfs_rqa;
struct cfs_rq *cfs_rqb;
s64 delta;
SCHED_WARN_ON(task_rq(b)->core != rq->core);
#ifdef CONFIG_FAIR_GROUP_SCHED
/*
* Find an se in the hierarchy for tasks a and b, such that the se's
* are immediate siblings.
*/
while (sea->cfs_rq->tg != seb->cfs_rq->tg) {
int sea_depth = sea->depth;
int seb_depth = seb->depth;
if (sea_depth >= seb_depth)
sea = parent_entity(sea);
if (sea_depth <= seb_depth)
seb = parent_entity(seb);
}
se_fi_update(sea, rq->core->core_forceidle_seq, in_fi);
se_fi_update(seb, rq->core->core_forceidle_seq, in_fi);
cfs_rqa = sea->cfs_rq;
cfs_rqb = seb->cfs_rq;
#else
cfs_rqa = &task_rq(a)->cfs;
cfs_rqb = &task_rq(b)->cfs;
#endif
/*
* Find delta after normalizing se's vruntime with its cfs_rq's
* min_vruntime_fi, which would have been updated in prior calls
* to se_fi_update().
*/
delta = (s64)(sea->vruntime - seb->vruntime) +
(s64)(cfs_rqb->min_vruntime_fi - cfs_rqa->min_vruntime_fi);
return delta > 0;
}
static int task_is_throttled_fair(struct task_struct *p, int cpu)
{
struct cfs_rq *cfs_rq;
#ifdef CONFIG_FAIR_GROUP_SCHED
cfs_rq = task_group(p)->cfs_rq[cpu];
#else
cfs_rq = &cpu_rq(cpu)->cfs;
#endif
return throttled_hierarchy(cfs_rq);
}
#else
static inline void task_tick_core(struct rq *rq, struct task_struct *curr) {}
#endif
/*
* scheduler tick hitting a task of our scheduling class.
*
* NOTE: This function can be called remotely by the tick offload that
* goes along full dynticks. Therefore no local assumption can be made
* and everything must be accessed through the @rq and @curr passed in
* parameters.
*/
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
{
struct cfs_rq *cfs_rq;
struct sched_entity *se = &curr->se;
for_each_sched_entity(se) {
cfs_rq = cfs_rq_of(se);
entity_tick(cfs_rq, se, queued);
}
if (static_branch_unlikely(&sched_numa_balancing))
task_tick_numa(rq, curr);
update_misfit_status(curr, rq);
update_overutilized_status(task_rq(curr));
task_tick_core(rq, curr);
}
/*
* called on fork with the child task as argument from the parent's context
* - child not yet on the tasklist
* - preemption disabled
*/
static void task_fork_fair(struct task_struct *p)
{
struct cfs_rq *cfs_rq;
struct sched_entity *se = &p->se, *curr;
struct rq *rq = this_rq();
struct rq_flags rf;
rq_lock(rq, &rf);
update_rq_clock(rq);
cfs_rq = task_cfs_rq(current);
curr = cfs_rq->curr;
if (curr) {
update_curr(cfs_rq);
se->vruntime = curr->vruntime;
}
place_entity(cfs_rq, se, 1);
if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
/*
* Upon rescheduling, sched_class::put_prev_task() will place
* 'current' within the tree based on its new key value.
*/
swap(curr->vruntime, se->vruntime);
resched_curr(rq);
}
se->vruntime -= cfs_rq->min_vruntime;
rq_unlock(rq, &rf);
}
/*
* Priority of the task has changed. Check to see if we preempt
* the current task.
*/
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
{
if (!task_on_rq_queued(p))
return;
if (rq->cfs.nr_running == 1)
return;
/*
* Reschedule if we are currently running on this runqueue and
* our priority decreased, or if we are not currently running on
* this runqueue and our priority is higher than the current's
*/
if (task_current(rq, p)) {
if (p->prio > oldprio)
resched_curr(rq);
} else
check_preempt_curr(rq, p, 0);
}
static inline bool vruntime_normalized(struct task_struct *p)
{
struct sched_entity *se = &p->se;
/*
* In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
* the dequeue_entity(.flags=0) will already have normalized the
* vruntime.
*/
if (p->on_rq)
return true;
/*
* When !on_rq, vruntime of the task has usually NOT been normalized.
* But there are some cases where it has already been normalized:
*
* - A forked child which is waiting for being woken up by
* wake_up_new_task().
* - A task which has been woken up by try_to_wake_up() and
* waiting for actually being woken up by sched_ttwu_pending().
*/
if (!se->sum_exec_runtime ||
(READ_ONCE(p->__state) == TASK_WAKING && p->sched_remote_wakeup))
return true;
return false;
}
#ifdef CONFIG_FAIR_GROUP_SCHED
/*
* Propagate the changes of the sched_entity across the tg tree to make it
* visible to the root
*/
static void propagate_entity_cfs_rq(struct sched_entity *se)
{
struct cfs_rq *cfs_rq = cfs_rq_of(se);
if (cfs_rq_throttled(cfs_rq))
return;
if (!throttled_hierarchy(cfs_rq))
list_add_leaf_cfs_rq(cfs_rq);
/* Start to propagate at parent */
se = se->parent;
for_each_sched_entity(se) {
cfs_rq = cfs_rq_of(se);
update_load_avg(cfs_rq, se, UPDATE_TG);
if (cfs_rq_throttled(cfs_rq))
break;
if (!throttled_hierarchy(cfs_rq))
list_add_leaf_cfs_rq(cfs_rq);
}
}
#else
static void propagate_entity_cfs_rq(struct sched_entity *se) { }
#endif
static void detach_entity_cfs_rq(struct sched_entity *se)
{
struct cfs_rq *cfs_rq = cfs_rq_of(se);
#ifdef CONFIG_SMP
/*
* In case the task sched_avg hasn't been attached:
* - A forked task which hasn't been woken up by wake_up_new_task().
* - A task which has been woken up by try_to_wake_up() but is
* waiting for actually being woken up by sched_ttwu_pending().
*/
if (!se->avg.last_update_time)
return;
#endif
/* Catch up with the cfs_rq and remove our load when we leave */
update_load_avg(cfs_rq, se, 0);
detach_entity_load_avg(cfs_rq, se);
update_tg_load_avg(cfs_rq);
propagate_entity_cfs_rq(se);
}
static void attach_entity_cfs_rq(struct sched_entity *se)
{
struct cfs_rq *cfs_rq = cfs_rq_of(se);
/* Synchronize entity with its cfs_rq */
update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
attach_entity_load_avg(cfs_rq, se);
update_tg_load_avg(cfs_rq);
propagate_entity_cfs_rq(se);
}
static void detach_task_cfs_rq(struct task_struct *p)
{
struct sched_entity *se = &p->se;
struct cfs_rq *cfs_rq = cfs_rq_of(se);
if (!vruntime_normalized(p)) {
/*
* Fix up our vruntime so that the current sleep doesn't
* cause 'unlimited' sleep bonus.
*/
place_entity(cfs_rq, se, 0);
se->vruntime -= cfs_rq->min_vruntime;
}
detach_entity_cfs_rq(se);
}
static void attach_task_cfs_rq(struct task_struct *p)
{
struct sched_entity *se = &p->se;
struct cfs_rq *cfs_rq = cfs_rq_of(se);
attach_entity_cfs_rq(se);
if (!vruntime_normalized(p))
se->vruntime += cfs_rq->min_vruntime;
}
static void switched_from_fair(struct rq *rq, struct task_struct *p)
{
detach_task_cfs_rq(p);
}
static void switched_to_fair(struct rq *rq, struct task_struct *p)
{
attach_task_cfs_rq(p);
if (task_on_rq_queued(p)) {
/*
* We were most likely switched from sched_rt, so
* kick off the schedule if running, otherwise just see
* if we can still preempt the current task.
*/
if (task_current(rq, p))
resched_curr(rq);
else
check_preempt_curr(rq, p, 0);
}
}
/* Account for a task changing its policy or group.
*
* This routine is mostly called to set cfs_rq->curr field when a task
* migrates between groups/classes.
*/
static void set_next_task_fair(struct rq *rq, struct task_struct *p, bool first)
{
struct sched_entity *se = &p->se;
#ifdef CONFIG_SMP
if (task_on_rq_queued(p)) {
/*
* Move the next running task to the front of the list, so our
* cfs_tasks list becomes MRU one.
*/
list_move(&se->group_node, &rq->cfs_tasks);
}
#endif
for_each_sched_entity(se) {
struct cfs_rq *cfs_rq = cfs_rq_of(se);
set_next_entity(cfs_rq, se);
/* ensure bandwidth has been allocated on our new cfs_rq */
account_cfs_rq_runtime(cfs_rq, 0);
}
}
void init_cfs_rq(struct cfs_rq *cfs_rq)
{
cfs_rq->tasks_timeline = RB_ROOT_CACHED;
u64_u32_store(cfs_rq->min_vruntime, (u64)(-(1LL << 20)));
#ifdef CONFIG_SMP
raw_spin_lock_init(&cfs_rq->removed.lock);
#endif
}
#ifdef CONFIG_FAIR_GROUP_SCHED
static void task_change_group_fair(struct task_struct *p)
{
/*
* We couldn't detach or attach a forked task which
* hasn't been woken up by wake_up_new_task().
*/
if (READ_ONCE(p->__state) == TASK_NEW)
return;
detach_task_cfs_rq(p);
#ifdef CONFIG_SMP
/* Tell se's cfs_rq has been changed -- migrated */
p->se.avg.last_update_time = 0;
#endif
set_task_rq(p, task_cpu(p));
attach_task_cfs_rq(p);
}
void free_fair_sched_group(struct task_group *tg)
{
int i;
for_each_possible_cpu(i) {
if (tg->cfs_rq)
kfree(tg->cfs_rq[i]);
if (tg->se)
kfree(tg->se[i]);
}
kfree(tg->cfs_rq);
kfree(tg->se);
}
int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
{
struct sched_entity *se;
struct cfs_rq *cfs_rq;
int i;
tg->cfs_rq = kcalloc(nr_cpu_ids, sizeof(cfs_rq), GFP_KERNEL);
if (!tg->cfs_rq)
goto err;
tg->se = kcalloc(nr_cpu_ids, sizeof(se), GFP_KERNEL);
if (!tg->se)
goto err;
tg->shares = NICE_0_LOAD;
init_cfs_bandwidth(tg_cfs_bandwidth(tg));
for_each_possible_cpu(i) {
cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
GFP_KERNEL, cpu_to_node(i));
if (!cfs_rq)
goto err;
se = kzalloc_node(sizeof(struct sched_entity_stats),
GFP_KERNEL, cpu_to_node(i));
if (!se)
goto err_free_rq;
init_cfs_rq(cfs_rq);
init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
init_entity_runnable_average(se);
}
return 1;
err_free_rq:
kfree(cfs_rq);
err:
return 0;
}
void online_fair_sched_group(struct task_group *tg)
{
struct sched_entity *se;
struct rq_flags rf;
struct rq *rq;
int i;
for_each_possible_cpu(i) {
rq = cpu_rq(i);
se = tg->se[i];
rq_lock_irq(rq, &rf);
update_rq_clock(rq);
attach_entity_cfs_rq(se);
sync_throttle(tg, i);
rq_unlock_irq(rq, &rf);
}
}
void unregister_fair_sched_group(struct task_group *tg)
{
unsigned long flags;
struct rq *rq;
int cpu;
destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
for_each_possible_cpu(cpu) {
if (tg->se[cpu])
remove_entity_load_avg(tg->se[cpu]);
/*
* Only empty task groups can be destroyed; so we can speculatively
* check on_list without danger of it being re-added.
*/
if (!tg->cfs_rq[cpu]->on_list)
continue;
rq = cpu_rq(cpu);
raw_spin_rq_lock_irqsave(rq, flags);
list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
raw_spin_rq_unlock_irqrestore(rq, flags);
}
}
void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
struct sched_entity *se, int cpu,
struct sched_entity *parent)
{
struct rq *rq = cpu_rq(cpu);
cfs_rq->tg = tg;
cfs_rq->rq = rq;
init_cfs_rq_runtime(cfs_rq);
tg->cfs_rq[cpu] = cfs_rq;
tg->se[cpu] = se;
/* se could be NULL for root_task_group */
if (!se)
return;
if (!parent) {
se->cfs_rq = &rq->cfs;
se->depth = 0;
} else {
se->cfs_rq = parent->my_q;
se->depth = parent->depth + 1;
}
se->my_q = cfs_rq;
/* guarantee group entities always have weight */
update_load_set(&se->load, NICE_0_LOAD);
se->parent = parent;
}
static DEFINE_MUTEX(shares_mutex);
static int __sched_group_set_shares(struct task_group *tg, unsigned long shares)
{
int i;
lockdep_assert_held(&shares_mutex);
/*
* We can't change the weight of the root cgroup.
*/
if (!tg->se[0])
return -EINVAL;
shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
if (tg->shares == shares)
return 0;
tg->shares = shares;
for_each_possible_cpu(i) {
struct rq *rq = cpu_rq(i);
struct sched_entity *se = tg->se[i];
struct rq_flags rf;
/* Propagate contribution to hierarchy */
rq_lock_irqsave(rq, &rf);
update_rq_clock(rq);
for_each_sched_entity(se) {
update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
update_cfs_group(se);
}
rq_unlock_irqrestore(rq, &rf);
}
return 0;
}
int sched_group_set_shares(struct task_group *tg, unsigned long shares)
{
int ret;
mutex_lock(&shares_mutex);
if (tg_is_idle(tg))
ret = -EINVAL;
else
ret = __sched_group_set_shares(tg, shares);
mutex_unlock(&shares_mutex);
return ret;
}
int sched_group_set_idle(struct task_group *tg, long idle)
{
int i;
if (tg == &root_task_group)
return -EINVAL;
if (idle < 0 || idle > 1)
return -EINVAL;
mutex_lock(&shares_mutex);
if (tg->idle == idle) {
mutex_unlock(&shares_mutex);
return 0;
}
tg->idle = idle;
for_each_possible_cpu(i) {
struct rq *rq = cpu_rq(i);
struct sched_entity *se = tg->se[i];
struct cfs_rq *parent_cfs_rq, *grp_cfs_rq = tg->cfs_rq[i];
bool was_idle = cfs_rq_is_idle(grp_cfs_rq);
long idle_task_delta;
struct rq_flags rf;
rq_lock_irqsave(rq, &rf);
grp_cfs_rq->idle = idle;
if (WARN_ON_ONCE(was_idle == cfs_rq_is_idle(grp_cfs_rq)))
goto next_cpu;
if (se->on_rq) {
parent_cfs_rq = cfs_rq_of(se);
if (cfs_rq_is_idle(grp_cfs_rq))
parent_cfs_rq->idle_nr_running++;
else
parent_cfs_rq->idle_nr_running--;
}
idle_task_delta = grp_cfs_rq->h_nr_running -
grp_cfs_rq->idle_h_nr_running;
if (!cfs_rq_is_idle(grp_cfs_rq))
idle_task_delta *= -1;
for_each_sched_entity(se) {
struct cfs_rq *cfs_rq = cfs_rq_of(se);
if (!se->on_rq)
break;
cfs_rq->idle_h_nr_running += idle_task_delta;
/* Already accounted at parent level and above. */
if (cfs_rq_is_idle(cfs_rq))
break;
}
next_cpu:
rq_unlock_irqrestore(rq, &rf);
}
/* Idle groups have minimum weight. */
if (tg_is_idle(tg))
__sched_group_set_shares(tg, scale_load(WEIGHT_IDLEPRIO));
else
__sched_group_set_shares(tg, NICE_0_LOAD);
mutex_unlock(&shares_mutex);
return 0;
}
#else /* CONFIG_FAIR_GROUP_SCHED */
void free_fair_sched_group(struct task_group *tg) { }
int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
{
return 1;
}
void online_fair_sched_group(struct task_group *tg) { }
void unregister_fair_sched_group(struct task_group *tg) { }
#endif /* CONFIG_FAIR_GROUP_SCHED */
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
{
struct sched_entity *se = &task->se;
unsigned int rr_interval = 0;
/*
* Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
* idle runqueue:
*/
if (rq->cfs.load.weight)
rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
return rr_interval;
}
/*
* All the scheduling class methods:
*/
DEFINE_SCHED_CLASS(fair) = {
.enqueue_task = enqueue_task_fair,
.dequeue_task = dequeue_task_fair,
.yield_task = yield_task_fair,
.yield_to_task = yield_to_task_fair,
.check_preempt_curr = check_preempt_wakeup,
.pick_next_task = __pick_next_task_fair,
.put_prev_task = put_prev_task_fair,
.set_next_task = set_next_task_fair,
#ifdef CONFIG_SMP
.balance = balance_fair,
.pick_task = pick_task_fair,
.select_task_rq = select_task_rq_fair,
.migrate_task_rq = migrate_task_rq_fair,
.rq_online = rq_online_fair,
.rq_offline = rq_offline_fair,
.task_dead = task_dead_fair,
.set_cpus_allowed = set_cpus_allowed_common,
#endif
.task_tick = task_tick_fair,
.task_fork = task_fork_fair,
.prio_changed = prio_changed_fair,
.switched_from = switched_from_fair,
.switched_to = switched_to_fair,
.get_rr_interval = get_rr_interval_fair,
.update_curr = update_curr_fair,
#ifdef CONFIG_FAIR_GROUP_SCHED
.task_change_group = task_change_group_fair,
#endif
#ifdef CONFIG_SCHED_CORE
.task_is_throttled = task_is_throttled_fair,
#endif
#ifdef CONFIG_UCLAMP_TASK
.uclamp_enabled = 1,
#endif
};
#ifdef CONFIG_SCHED_DEBUG
void print_cfs_stats(struct seq_file *m, int cpu)
{
struct cfs_rq *cfs_rq, *pos;
rcu_read_lock();
for_each_leaf_cfs_rq_safe(cpu_rq(cpu), cfs_rq, pos)
print_cfs_rq(m, cpu, cfs_rq);
rcu_read_unlock();
}
#ifdef CONFIG_NUMA_BALANCING
void show_numa_stats(struct task_struct *p, struct seq_file *m)
{
int node;
unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
struct numa_group *ng;
rcu_read_lock();
ng = rcu_dereference(p->numa_group);
for_each_online_node(node) {
if (p->numa_faults) {
tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
}
if (ng) {
gsf = ng->faults[task_faults_idx(NUMA_MEM, node, 0)],
gpf = ng->faults[task_faults_idx(NUMA_MEM, node, 1)];
}
print_numa_stats(m, node, tsf, tpf, gsf, gpf);
}
rcu_read_unlock();
}
#endif /* CONFIG_NUMA_BALANCING */
#endif /* CONFIG_SCHED_DEBUG */
__init void init_sched_fair_class(void)
{
#ifdef CONFIG_SMP
int i;
for_each_possible_cpu(i) {
zalloc_cpumask_var_node(&per_cpu(load_balance_mask, i), GFP_KERNEL, cpu_to_node(i));
zalloc_cpumask_var_node(&per_cpu(select_rq_mask, i), GFP_KERNEL, cpu_to_node(i));
#ifdef CONFIG_CFS_BANDWIDTH
INIT_CSD(&cpu_rq(i)->cfsb_csd, __cfsb_csd_unthrottle, cpu_rq(i));
INIT_LIST_HEAD(&cpu_rq(i)->cfsb_csd_list);
#endif
}
open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
#ifdef CONFIG_NO_HZ_COMMON
nohz.next_balance = jiffies;
nohz.next_blocked = jiffies;
zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
#endif
#endif /* SMP */
}
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