On 4/26/23 07:57, Juri Lelli wrote:
On 04/04/23 13:31, Waiman Long wrote:
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@xxxxxxxxxx>
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.
I'm not a big fan of rwsems for reasons like
https://lore.kernel.org/lkml/20230321161140.HMcQEhHb@xxxxxxxxxxxxx/, so
I'd vote for a standard mutex unless we have a strong argument and/or
numbers.
That is fine for me too.
Cheers,
Longman
