linux-kernel - Re: [PATCH v8 5/6] cgroup/cpuset: Update description of cpuset.cpus.partition in cgroup-v2.rst

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Message-ID: <e16ccf4f-7302-8891-d9f6-081e0bc41c04@redhat.com>
Date:   Wed, 1 Dec 2021 12:49:15 -0500
From:   Waiman Long <longman@...hat.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     Michal Koutný <mkoutny@...e.com>,
        Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Jonathan Corbet <corbet@....net>,
        Shuah Khan <shuah@...nel.org>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kselftest@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <guro@...com>, Phil Auld <pauld@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Marcelo Tosatti <mtosatti@...hat.com>
Subject: Re: [PATCH v8 5/6] cgroup/cpuset: Update description of
 cpuset.cpus.partition in cgroup-v2.rst


On 12/1/21 11:39, Tejun Heo wrote:
> On Wed, Dec 01, 2021 at 09:56:21AM -0500, Waiman Long wrote:
>> Right, I shouldn't say corner cases. Having task in an intermediate
>> partition is possible depending on event sequence. I am aware that there are
>> code in the cpuset code to prevent that, but it didn't block all cases.
>>>> A valid parent partition may distribute out all its CPUs to
>>>>    its child partitions as long as there is no task associated with it.
>>> Assuming there's always at least one kernel thread in the root cgroup
>>> that can't be migrated anyway.]
>> I am aware of that. That is why I said root cgroup must have at least one
>> cpu in its "cpuset.cpus.effective".
> In that case, let's explicitly describe that condition.

Yes, I will. Only non-root cgroup can distribute out all its CPUs. I 
thought I said that in the documentation, maybe it is very clear.

Cheers,
Longman