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sched_deadline, docs: add affinity setting with cgroup2 cpuset controller

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Setting the cpu affinity mask of a SCHED_DEADLINE process using the cgroup v1
cpuset controller is already detailed. Add similar information for cgroup v2's
cpuset controller.

Signed-off-by: Shashank Balaji <shashank.mahadasyam@sony.com>
Reviewed-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20250527-sched-deadline-cpu-affinity-v2-2-b8b40a4feefa@sony.com
This commit is contained in:
Shashank Balaji
2025-05-27 23:55:58 +09:00
committed by Jonathan Corbet
parent ab8531cdb1
commit 0116765035
1 changed files with 23 additions and 6 deletions
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29
Documentation/scheduler/sched-deadline.rst
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@@ -20,7 +20,8 @@ Deadline Task Scheduling
4.3 Default behavior
4.4 Behavior of sched_yield()
5. Tasks CPU affinity
5.1 SCHED_DEADLINE and cpusets HOWTO
5.1 Using cgroup v1 cpuset controller
5.2 Using cgroup v2 cpuset controller
6. Future plans
A. Test suite
B. Minimal main()
@@ -671,12 +672,15 @@ Deadline Task Scheduling
5. Tasks CPU affinity
=====================
-deadline tasks cannot have an affinity mask smaller that the entire
root_domain they are created on. However, affinities can be specified
through the cpuset facility (Documentation/admin-guide/cgroup-v1/cpusets.rst).
Deadline tasks cannot have a cpu affinity mask smaller than the root domain they
are created on. So, using ``sched_setaffinity(2)`` won't work. Instead, the
the deadline task should be created in a restricted root domain. This can be
done using the cpuset controller of either cgroup v1 (deprecated) or cgroup v2.
See :ref:`Documentation/admin-guide/cgroup-v1/cpusets.rst <cpusets>` and
:ref:`Documentation/admin-guide/cgroup-v2.rst <cgroup-v2>` for more information.
5.1 SCHED_DEADLINE and cpusets HOWTO
------------------------------------
5.1 Using cgroup v1 cpuset controller
-------------------------------------
An example of a simple configuration (pin a -deadline task to CPU0) follows::
@@ -693,6 +697,19 @@ Deadline Task Scheduling
echo $$ > cpu0/tasks
chrt --sched-runtime 100000 --sched-period 200000 --deadline 0 yes > /dev/null
5.2 Using cgroup v2 cpuset controller
-------------------------------------
Assuming the cgroup v2 root is mounted at ``/sys/fs/cgroup``.
cd /sys/fs/cgroup
echo '+cpuset' > cgroup.subtree_control
mkdir deadline_group
echo 0 > deadline_group/cpuset.cpus
echo 'root' > deadline_group/cpuset.cpus.partition
echo $$ > deadline_group/cgroup.procs
chrt --sched-runtime 100000 --sched-period 200000 --deadline 0 yes > /dev/null
6. Future plans
===============