linux-kernel - Re: [PATCH v7 0/5] cpuset: Enable cpuset controller in default hierarchy

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Date:   Mon, 23 Apr 2018 10:10:39 -0400
From:   Waiman Long <longman@...hat.com>
To:     Juri Lelli <juri.lelli@...hat.com>
Cc:     Tejun Heo <tj@...nel.org>, 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>
Subject: Re: [PATCH v7 0/5] cpuset: Enable cpuset controller in default
 hierarchy

On 04/23/2018 09:57 AM, Juri Lelli wrote:
> On 23/04/18 15:07, Juri Lelli wrote:
>> Hi Waiman,
>>
>> On 19/04/18 09:46, Waiman Long wrote:
>>> v7:
>>>  - Add a root-only cpuset.cpus.isolated control file for CPU isolation.
>>>  - Enforce that load_balancing can only be turned off on cpusets with
>>>    CPUs from the isolated list.
>>>  - Update sched domain generation to allow cpusets with CPUs only
>>>    from the isolated CPU list to be in separate root domains.
> Guess I'll be adding comments as soon as I stumble on something unclear
> (to me :), hope that's OK (shout if I should do it differently).
>
> The below looked unexpected to me:
>
> root@...ian-kvm:/sys/fs/cgroup# cat g1/cpuset.cpus
> 2-3
> root@...ian-kvm:/sys/fs/cgroup# cat g1/cpuset.mems
>
> root@...ian-kvm:~# echo $$ > /sys/fs/cgroup/g1/cgroup.threads
> root@...ian-kvm:/sys/fs/cgroup# cat g1/cgroup.threads
> 2312
>
> So I can add tasks to groups with no mems? Or is it this only true in my
> case with a single mem node? Or maybe it's inherited from root group
> (slightly confusing IMHO if that's the case).

No mems mean looking up the parents until we find one with non-empty
mems. The mems.effective will show you the actual memory nodes used.

-Longman