From: Waiman Long <llong@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: "Zefan Li" <lizefan.x@bytedance.com>,
"Johannes Weiner" <hannes@cmpxchg.org>,
"Jonathan Corbet" <corbet@lwn.net>,
"Shuah Khan" <shuah@kernel.org>,
cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org,
"Andrew Morton" <akpm@linux-foundation.org>,
"Roman Gushchin" <guro@fb.com>, "Phil Auld" <pauld@redhat.com>,
"Peter Zijlstra" <peterz@infradead.org>,
"Juri Lelli" <juri.lelli@redhat.com>,
"Frederic Weisbecker" <frederic@kernel.org>,
"Marcelo Tosatti" <mtosatti@redhat.com>,
"Michal Koutný" <mkoutny@suse.com>
Subject: Re: [PATCH v4 4/6] cgroup/cpuset: Allow non-top parent partition root to distribute out all CPUs
Date: Wed, 11 Aug 2021 14:18:17 -0400 [thread overview]
Message-ID: <abfa6f2f-aa13-f18e-5a16-f568082d07bc@redhat.com> (raw)
In-Reply-To: <YRQTTf+bJZ8f3O3+@slm.duckdns.org>
On 8/11/21 2:13 PM, Tejun Heo wrote:
> On Tue, Aug 10, 2021 at 11:06:05PM -0400, Waiman Long wrote:
>> Currently, a parent partition root cannot distribute all its CPUs to
>> child partition roots with no CPUs left. However in some use cases,
>> a management application may want to create a parent partition root as
>> a management unit with no task associated with it and has all its CPUs
>> distributed to various child partition roots dynamically according to
>> their needs. Leaving a cpu in the parent partition root in such a case is
>> now a waste.
>>
>> To accommodate such use cases, a parent partition root can now have
>> all its CPUs distributed to its child partition roots as long as:
>> 1) it is not the top cpuset; and
>> 2) there is no task directly associated with the parent.
>>
>> Once an empty parent partition root is formed, no new task can be moved
>> into it.
> The above are already enforced by cgroup2 core, right? No intermediate
> cgroup with controllers enabled can have processes. From controllers' POV,
> only leaves can have processes.
>
I don't think that is true. A task can reside anywhere in the cgroup
hierarchy. I have encountered no problem moving tasks around.
Cheers,
Longman
next prev parent reply other threads:[~2021-08-11 18:18 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-11 3:06 [PATCH-cgroup v4 0/6] cgroup/cpuset: Add new cpuset partition type & empty effecitve cpus Waiman Long
2021-08-11 3:06 ` [PATCH v4 1/6] cgroup/cpuset: Enable event notification when partition state changes Waiman Long
2021-08-11 18:04 ` Tejun Heo
2021-08-11 3:06 ` [PATCH v4 2/6] cgroup/cpuset: Properly handle partition root tree Waiman Long
2021-08-11 18:08 ` Tejun Heo
2021-08-11 19:27 ` Waiman Long
2021-08-12 22:18 ` Tejun Heo
2021-08-12 22:56 ` Waiman Long
2021-08-13 16:07 ` Tejun Heo
2021-08-11 3:06 ` [PATCH v4 3/6] cgroup/cpuset: Add a new isolated cpus.partition type Waiman Long
2021-08-11 3:06 ` [PATCH v4 4/6] cgroup/cpuset: Allow non-top parent partition root to distribute out all CPUs Waiman Long
2021-08-11 18:13 ` Tejun Heo
2021-08-11 18:18 ` Waiman Long [this message]
2021-08-11 18:21 ` Tejun Heo
2021-08-11 18:46 ` Waiman Long
2021-08-12 21:51 ` Tejun Heo
2021-08-11 3:06 ` [PATCH v4 5/6] cgroup/cpuset: Update description of cpuset.cpus.partition in cgroup-v2.rst Waiman Long
2021-08-11 18:15 ` Tejun Heo
2021-08-11 18:19 ` Waiman Long
2021-08-11 3:06 ` [PATCH v4 6/6] kselftest/cgroup: Add cpuset v2 partition root state test Waiman Long
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