79 lines
3.2 KiB
ReStructuredText
79 lines
3.2 KiB
ReStructuredText
|
.. SPDX-License-Identifier: GPL-2.0
|
||
|
|
|
||
|
|
=====================
|
||
|
|
Fake NUMA For CPUSets
|
||
|
|
=====================
|
||
|
|
|
||
|
|
:Author: David Rientjes <rientjes@cs.washington.edu>
|
||
|
|
|
||
|
|
Using numa=fake and CPUSets for Resource Management
|
||
|
|
|
||
|
|
This document describes how the numa=fake x86_64 command-line option can be used
|
||
|
|
in conjunction with cpusets for coarse memory management. Using this feature,
|
||
|
|
you can create fake NUMA nodes that represent contiguous chunks of memory and
|
||
|
|
assign them to cpusets and their attached tasks. This is a way of limiting the
|
||
|
|
amount of system memory that are available to a certain class of tasks.
|
||
|
|
|
||
|
|
For more information on the features of cpusets, see
|
||
|
|
Documentation/admin-guide/cgroup-v1/cpusets.rst.
|
||
|
|
There are a number of different configurations you can use for your needs. For
|
||
|
|
more information on the numa=fake command line option and its various ways of
|
||
|
|
configuring fake nodes, see Documentation/x86/x86_64/boot-options.rst.
|
||
|
|
|
||
|
|
For the purposes of this introduction, we'll assume a very primitive NUMA
|
||
|
|
emulation setup of "numa=fake=4*512,". This will split our system memory into
|
||
|
|
four equal chunks of 512M each that we can now use to assign to cpusets. As
|
||
|
|
you become more familiar with using this combination for resource control,
|
||
|
|
you'll determine a better setup to minimize the number of nodes you have to deal
|
||
|
|
with.
|
||
|
|
|
||
|
|
A machine may be split as follows with "numa=fake=4*512," as reported by dmesg::
|
||
|
|
|
||
|
|
Faking node 0 at 0000000000000000-0000000020000000 (512MB)
|
||
|
|
Faking node 1 at 0000000020000000-0000000040000000 (512MB)
|
||
|
|
Faking node 2 at 0000000040000000-0000000060000000 (512MB)
|
||
|
|
Faking node 3 at 0000000060000000-0000000080000000 (512MB)
|
||
|
|
...
|
||
|
|
On node 0 totalpages: 130975
|
||
|
|
On node 1 totalpages: 131072
|
||
|
|
On node 2 totalpages: 131072
|
||
|
|
On node 3 totalpages: 131072
|
||
|
|
|
||
|
|
Now following the instructions for mounting the cpusets filesystem from
|
||
|
|
Documentation/admin-guide/cgroup-v1/cpusets.rst, you can assign fake nodes (i.e. contiguous memory
|
||
|
|
address spaces) to individual cpusets::
|
||
|
|
|
||
|
|
[root@xroads /]# mkdir exampleset
|
||
|
|
[root@xroads /]# mount -t cpuset none exampleset
|
||
|
|
[root@xroads /]# mkdir exampleset/ddset
|
||
|
|
[root@xroads /]# cd exampleset/ddset
|
||
|
|
[root@xroads /exampleset/ddset]# echo 0-1 > cpus
|
||
|
|
[root@xroads /exampleset/ddset]# echo 0-1 > mems
|
||
|
|
|
||
|
|
Now this cpuset, 'ddset', will only allowed access to fake nodes 0 and 1 for
|
||
|
|
memory allocations (1G).
|
||
|
|
|
||
|
|
You can now assign tasks to these cpusets to limit the memory resources
|
||
|
|
available to them according to the fake nodes assigned as mems::
|
||
|
|
|
||
|
|
[root@xroads /exampleset/ddset]# echo $$ > tasks
|
||
|
|
[root@xroads /exampleset/ddset]# dd if=/dev/zero of=tmp bs=1024 count=1G
|
||
|
|
[1] 13425
|
||
|
|
|
||
|
|
Notice the difference between the system memory usage as reported by
|
||
|
|
/proc/meminfo between the restricted cpuset case above and the unrestricted
|
||
|
|
case (i.e. running the same 'dd' command without assigning it to a fake NUMA
|
||
|
|
cpuset):
|
||
|
|
|
||
|
|
======== ============ ==========
|
||
|
|
Name Unrestricted Restricted
|
||
|
|
======== ============ ==========
|
||
|
|
MemTotal 3091900 kB 3091900 kB
|
||
|
|
MemFree 42113 kB 1513236 kB
|
||
|
|
======== ============ ==========
|
||
|
|
|
||
|
|
This allows for coarse memory management for the tasks you assign to particular
|
||
|
|
cpusets. Since cpusets can form a hierarchy, you can create some pretty
|
||
|
|
interesting combinations of use-cases for various classes of tasks for your
|
||
|
|
memory management needs.
|