linux-kernel - Re: [PATCH v9 0/7] Enable cpuset controller in default hierarchy

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Date:   Wed, 30 May 2018 08:56:10 -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>,
        Patrick Bellasi <patrick.bellasi@....com>
Subject: Re: [PATCH v9 0/7] Enable cpuset controller in default hierarchy

On 05/30/2018 06:13 AM, Juri Lelli wrote:
> Hi,
>
> On 29/05/18 09:41, Waiman Long wrote:
>> v9:
>>  - Rename cpuset.sched.domain to cpuset.sched.domain_root to better
>>    identify its purpose as the root of a new scheduling domain or
>>    partition.
>>  - Clarify in the document about the purpose of domain_root and
>>    load_balance. Using domain_root is th only way to create new
>>    partition.
>>  - Fix a lockdep warning in update_isolated_cpumask() function.
>>  - Add a new patch to eliminate call to generate_sched_domains() for
>>    v2 when a change in cpu list does not touch a domain_root.
> I was playing with this and ended up with the situation below:
>
>  g1/cgroup.controllers:cpuset
>  g1/cgroup.events:populated 0
>  g1/cgroup.max.depth:max
>  g1/cgroup.max.descendants:max
>  g1/cgroup.stat:nr_descendants 1
>  g1/cgroup.stat:nr_dying_descendants 0
>  g1/cgroup.subtree_control:cpuset
>  g1/cgroup.type:domain
>  g1/cpuset.cpus:0-5                   <---
>  g1/cpuset.cpus.effective:0-5
>  g1/cpuset.mems.effective:0-1
>  g1/cpuset.sched.domain_root:1        <---
>  g1/cpuset.sched.load_balance:1
>  g1/cpu.stat:usage_usec 0
>  g1/cpu.stat:user_usec 0
>  g1/cpu.stat:system_usec 0
>  g1/g11/cgroup.events:populated 0
>  g1/g11/cgroup.max.descendants:max
>  g1/g11/cpu.stat:usage_usec 0
>  g1/g11/cpu.stat:user_usec 0
>  g1/g11/cpu.stat:system_usec 0
>  g1/g11/cgroup.type:domain
>  g1/g11/cgroup.stat:nr_descendants 0
>  g1/g11/cgroup.stat:nr_dying_descendants 0
>  g1/g11/cpuset.cpus.effective:0-5
>  g1/g11/cgroup.controllers:cpuset
>  g1/g11/cpuset.sched.load_balance:1
>  g1/g11/cpuset.mems.effective:0-1
>  g1/g11/cpuset.cpus:6-11              <---
>  g1/g11/cgroup.max.depth:max
>  g1/g11/cpuset.sched.domain_root:0
>
> Should this be allowed? I was expecting subgroup g11 should be
> restricted to a subset of g1's cpus.
>
> Best,
>
> - Juri

That shouldn't be allowed.The code is probably missing some checks that
should have been done. What was the sequence of commands leading to the
above configuration?

Cheers,
Longman