Re: [PATCH 2/6] sched/cpuset: Bring back cpuset_mutex

Waiman Long
2023-04-04T17:31:51Z

On 3/29/23 08:55, Juri Lelli wrote:
> Turns out percpu_cpuset_rwsem - commit 1243dc518c9d ("cgroup/cpuset:
> Convert cpuset_mutex to percpu_rwsem") - wasn't such a brilliant idea,
> as it has been reported to cause slowdowns in workloads that need to
> change cpuset configuration frequently and it is also not implementing
> priority inheritance (which causes troubles with realtime workloads).
>
> Convert percpu_cpuset_rwsem back to regular cpuset_mutex. Also grab it
> only for SCHED_DEADLINE tasks (other policies don't care about stable
> cpusets anyway).
>
> Signed-off-by: Juri Lelli <juri.lelli-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

I am thinking that maybe we should switch the percpu rwsem to a regular
rwsem as there are cases where a read lock is sufficient. This will also
avoid the potential PREEMPT_RT problem with PI and reduce the time it
needs to take a write lock.

Cheers,
Longman