Re: [PATCH v2] sched: async unthrottling for cfs bandwidth

[Tejun Heo]

Hello,

On Tue, Nov 01, 2022 at 12:11:30PM -0700, Josh Don wrote:
> > Just to better understand the situation, can you give some more details on
> > the scenarios where cgroup_mutex was in the middle of a shitshow?
> 
> There have been a couple, I think one of the main ones has been writes
> to cgroup.procs. cpuset modifications also show up since there's a
> mutex there.

If you can, I'd really like to learn more about the details. We've had some
issues with the threadgroup_rwsem because it's such a big hammer but not
necessarily with cgroup_mutex because they are only used in maintenance
operations and never from any hot paths.

Regarding threadgroup_rwsem, w/ CLONE_INTO_CGROUP (userspace support is
still missing unfortunately), the usual worfklow of creating a cgroup,
seeding it with a process and then later shutting it down doesn't involve
threadgroup_rwsem at all, so most of the problems should go away in the
hopefully near future.

Thanks.

-- 
tejun