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

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Date:   Fri, 17 Aug 2018 08:59:46 -0700
From:   Tejun Heo <tj@...nel.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.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 Mon, Aug 13, 2018 at 01:56:15PM -0400, Waiman Long wrote:
> The following restrictions are still imposed on a partition root wrt
> allowable changes in cpuset.cpus:
> 1) cpuset.cpus cannot be set to "". There must be at least 1 cpu there.
> 2) Adding cpus that are not in parent's cpuset.cpus (as well as
> cpuset.cpus.effective) or that will take all the parent's effective cpus
> away is not allowed.
> 
> So are these limitations acceptable?
> 
> The easiest way to remove those restrictions is to forcefully turn off
> the cpuset.sched.partition flag in the cpuset as well as any
> sub-partitions when the user try to do that. With that change, there
> will be no more new restriction on what you can do on cpuset.cpus.

I think that'd be the right thing to do.  That's what we do with
cpuset.cpus and cpuset.mems too.  If there's nothing available, we
ignore the config and show the settings which are currently in effect.

Thanks.

-- 
tejun