Messages in this thread | | | Date | Mon, 25 Jul 2022 16:16:49 +0200 | From | Christian Brauner <> | Subject | Re: [PATCH RESEND 3/3 cgroup/for-5.20] cgroup: Make !percpu threadgroup_rwsem operations optional |
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On Sat, Jul 23, 2022 at 04:28:28AM -1000, Tejun Heo wrote: > 3942a9bd7b58 ("locking, rcu, cgroup: Avoid synchronize_sched() in > __cgroup_procs_write()") disabled percpu operations on threadgroup_rwsem > because the impiled synchronize_rcu() on write locking was pushing up the > latencies too much for android which constantly moves processes between > cgroups. > > This makes the hotter paths - fork and exit - slower as they're always > forced into the slow path. There is no reason to force this on everyone > especially given that more common static usage pattern can now completely > avoid write-locking the rwsem. Write-locking is elided when turning on and > off controllers on empty sub-trees and CLONE_INTO_CGROUP enables seeding a > cgroup without grabbing the rwsem. > > Restore the default percpu operations and introduce the mount option > "favordynmods" and config option CGROUP_FAVOR_DYNMODS for users who need > lower latencies for the dynamic operations. > > Signed-off-by: Tejun Heo <tj@kernel.org> > Cc: Christian Brauner <brauner@kernel.org> > Cc: Michal Koutný <mkoutny@suse.com> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: John Stultz <john.stultz@linaro.org> > Cc: Dmitry Shmidt <dimitrysh@google.com> > Cc: Oleg Nesterov <oleg@redhat.com> > ---
Seems sane, Acked-by: Christian Brauner (Microsoft) <brauner@kernel.org>
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