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

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Date:   Fri, 20 Jul 2018 13:31:21 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Tejun Heo <tj@...nel.org>
Cc:     Waiman Long <longman@...hat.com>, 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

On Thu, Jul 19, 2018 at 09:52:01AM -0700, Tejun Heo wrote:
> Hello,
> 
> On Thu, Jul 19, 2018 at 11:52:46AM -0400, Waiman Long wrote:
> > BTW, the way the partition is currently implemented right now is that a
> > child cannot be a partition root unless its parent is a partition root
> > itself. That is to avoid turning on partition to affect ancestors
> > further up the hierarchy than just the parent. So in the case of a
> > container, it cannot allocate sub-partitions underneath it unless it is
> > a partition itself. Will that solve your concern?
> 
> Hmm... so a given ancestor must be able to both
> 
> 1. control which cpus are moved into a partition in all of its
>    subtree.

By virtue of the partition file being owned by the parent, this is
already achived, no?

> 2. take away any given cpu from ist subtree.

I really hate this obsession of yours and doubly so for partitions. But
why would this currently not be allowed?