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

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Message-ID: <20180719172551.GW72677@devbig577.frc2.facebook.com>
Date:   Thu, 19 Jul 2018 10:25:51 -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 Thu, Jul 19, 2018 at 01:22:36PM -0400, Waiman Long wrote:
...
> Do you want a way at the parent level to take CPUs away from child
> partitions? The "cpus.subpart" file can probably be used also for this
> purpose, but we have to decide what taking CPUs away from child
> partition means. Does that mean automatically turn off the partition
> flag in the children if there is no CPU left in the partition? There are

Yeah, I think so.  That's what we do when cpuset.cpus or mems go empty
- ignoring the config.

> some implementation details that need to be fleshed out. I would prefer
> not doing this as this will complicate the code without too much benefit
> that I can see.

So, given how long this has been dragging along and it isn't yet super
clear to me why this needs to be fully hierarchical, I'd actually
prefer just restricting it to the first level children.

Thanks.

-- 
tejun