linux-kernel - Re: [PATCH v11 7/9] cpuset: Expose cpus.effective and mems.effective on cgroup v2 root

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Message-ID: <20180703155823.GS533219@devbig577.frc2.facebook.com>
Date:   Tue, 3 Jul 2018 08:58:23 -0700
From:   Tejun Heo <tj@...nel.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        kernel-team@...com, pjt@...gle.com, luto@...capital.net,
        Mike Galbraith <efault@....de>, torvalds@...ux-foundation.org,
        Roman Gushchin <guro@...com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Patrick Bellasi <patrick.bellasi@....com>
Subject: Re: [PATCH v11 7/9] cpuset: Expose cpus.effective and mems.effective
 on cgroup v2 root

Hello, Waiman.

On Tue, Jul 03, 2018 at 08:41:31AM +0800, Waiman Long wrote:
> > So, effective changing when enabling partition on a child feels wrong
> > to me.  It's supposed to contain what's actually allowed to the cgroup
> > from its parent and that shouldn't change regardless of how those
> > resources are used.  It's still given to the cgroup from its parent.
> 
> Another way to work around this issue is to expose the reserved_cpus in
> the parent for holding CPUs that can taken by a chid partition. That
> will require adding one more cpuset file for those cgroups that are
> partition roots.

Yeah, that should work.

> I don't mind restricting that to the first level children for now. That
> does restrict where we can put the container root if we want a separate
> partition for a container. Let's hear if others have any objection about
> that.

As currently implemented, partioning locks away the cpus which should
be a system level decision, not container level, so it makes sense to
me that it is only available to system root.

Thanks.

-- 
tejun