From: Waiman Long <longman@redhat.com> To: "Michal Koutný" <mkoutny@suse.com> Cc: Tejun Heo <tj@kernel.org>, 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> Subject: Re: [PATCH v8 5/6] cgroup/cpuset: Update description of cpuset.cpus.partition in cgroup-v2.rst Date: Wed, 1 Dec 2021 09:56:21 -0500 [thread overview] Message-ID: <ec6e2b89-385a-fcc7-7cfa-7e9119fc34bc@redhat.com> (raw) In-Reply-To: <20211201141350.GA54766@blackbody.suse.cz> On 12/1/21 09:13, Michal Koutný wrote: > On Tue, Nov 30, 2021 at 10:56:34PM -0500, Waiman Long <longman@redhat.com> wrote: >>>> A valid parent partition may distribute out all its CPUs to >>>> its child partitions as long as it is not the root cgroup and >>>> there is no task associated with it. >>> A valid parent partition which isn't root never has tasks in them to begin >>> with. >> I believe there is some corner cases where it is possible to put task in an >> intermediate partition. That is why I put down this statement. > Just mind the threads -- cpuset controller is threaded and having tasks > in inner cgroup nodes is a real scenario. I wouldn't consider it a > corner case. > > [ Actually, the paragraph could IMO be simplified: 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". Cheers, Longman
WARNING: multiple messages have this Message-ID (diff)
From: Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> To: "Michal Koutný" <mkoutny-IBi9RG/b67k@public.gmane.org> Cc: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Zefan Li <lizefan.x-EC8Uxl6Npydl57MIdRCFDg@public.gmane.org>, Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>, Jonathan Corbet <corbet-T1hC0tSOHrs@public.gmane.org>, Shuah Khan <shuah-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kselftest-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Roman Gushchin <guro-b10kYP2dOMg@public.gmane.org>, Phil Auld <pauld-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>, Juri Lelli <juri.lelli-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Frederic Weisbecker <frederic-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Marcelo Tosatti <mtosatti-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Subject: Re: [PATCH v8 5/6] cgroup/cpuset: Update description of cpuset.cpus.partition in cgroup-v2.rst Date: Wed, 1 Dec 2021 09:56:21 -0500 [thread overview] Message-ID: <ec6e2b89-385a-fcc7-7cfa-7e9119fc34bc@redhat.com> (raw) In-Reply-To: <20211201141350.GA54766-9OudH3eul5jcvrawFnH+a6VXKuFTiq87@public.gmane.org> On 12/1/21 09:13, Michal Koutný wrote: > On Tue, Nov 30, 2021 at 10:56:34PM -0500, Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote: >>>> A valid parent partition may distribute out all its CPUs to >>>> its child partitions as long as it is not the root cgroup and >>>> there is no task associated with it. >>> A valid parent partition which isn't root never has tasks in them to begin >>> with. >> I believe there is some corner cases where it is possible to put task in an >> intermediate partition. That is why I put down this statement. > Just mind the threads -- cpuset controller is threaded and having tasks > in inner cgroup nodes is a real scenario. I wouldn't consider it a > corner case. > > [ Actually, the paragraph could IMO be simplified: 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". Cheers, Longman
next prev parent reply other threads:[~2021-12-01 14:57 UTC|newest] Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-10-18 14:36 [PATCH v8 0/6] cgroup/cpuset: Add new cpuset partition type & empty effecitve cpus Waiman Long 2021-10-18 14:36 ` Waiman Long 2021-10-18 14:36 ` [PATCH v8 1/6] cgroup/cpuset: Allow no-task partition to have empty cpuset.cpus.effective Waiman Long 2021-10-18 14:36 ` Waiman Long 2021-10-18 14:36 ` [PATCH v8 2/6] cgroup/cpuset: Refining features and constraints of a partition Waiman Long 2021-10-18 14:36 ` Waiman Long 2021-10-18 14:36 ` [PATCH v8 3/6] cgroup/cpuset: Add a new isolated cpus.partition type Waiman Long 2021-10-18 14:36 ` [PATCH v8 4/6] cgroup/cpuset: Show invalid partition reason string Waiman Long 2021-10-18 14:36 ` [PATCH v8 5/6] cgroup/cpuset: Update description of cpuset.cpus.partition in cgroup-v2.rst Waiman Long 2021-11-15 19:31 ` Michal Koutný 2021-11-15 19:31 ` Michal Koutný 2021-11-15 20:11 ` Tejun Heo 2021-11-15 20:11 ` Tejun Heo 2021-11-15 21:27 ` Waiman Long 2021-11-15 21:27 ` Waiman Long 2021-11-15 21:10 ` Waiman Long 2021-11-16 17:54 ` Michal Koutný 2021-11-30 15:35 ` Waiman Long 2021-11-30 17:11 ` Tejun Heo 2021-11-30 17:11 ` Tejun Heo 2021-12-01 3:56 ` Waiman Long 2021-12-01 14:13 ` Michal Koutný 2021-12-01 14:13 ` Michal Koutný 2021-12-01 14:56 ` Waiman Long [this message] 2021-12-01 14:56 ` Waiman Long 2021-12-01 16:39 ` Tejun Heo 2021-12-01 17:49 ` Waiman Long 2021-12-01 17:49 ` Waiman Long 2021-12-01 14:26 ` Waiman Long 2021-12-01 14:26 ` Waiman Long 2021-12-01 16:46 ` Tejun Heo 2021-12-01 16:46 ` Tejun Heo 2021-12-01 18:05 ` Waiman Long 2021-12-02 1:28 ` Waiman Long 2021-12-03 18:25 ` Michal Koutný 2021-12-03 18:25 ` Michal Koutný 2021-12-03 19:27 ` Waiman Long 2021-10-18 14:36 ` [PATCH v8 6/6] kselftest/cgroup: Add cpuset v2 partition root state test Waiman Long 2021-10-18 14:36 ` Waiman Long 2021-10-27 23:05 ` [PATCH v8 0/6] cgroup/cpuset: Add new cpuset partition type & empty effecitve cpus Waiman Long 2021-11-10 11:13 ` Felix Moessbauer 2021-11-10 13:21 ` Marcelo Tosatti 2021-11-10 13:56 ` Michal Koutný 2021-11-10 15:21 ` Moessbauer, Felix 2021-11-10 15:21 ` Moessbauer, Felix 2021-11-10 16:10 ` Marcelo Tosatti 2021-11-10 16:10 ` Marcelo Tosatti 2021-11-10 16:14 ` Marcelo Tosatti 2021-11-10 16:14 ` Marcelo Tosatti 2021-11-10 16:15 ` Jan Kiszka 2021-11-10 16:15 ` Jan Kiszka 2021-11-10 17:29 ` Marcelo Tosatti 2021-11-10 17:29 ` Marcelo Tosatti 2021-11-10 18:30 ` Waiman Long 2021-11-10 18:30 ` Waiman Long 2021-11-10 17:52 ` Michal Koutný 2021-11-10 17:52 ` Michal Koutný 2021-11-10 18:04 ` Jan Kiszka 2021-11-10 18:04 ` Jan Kiszka 2021-11-10 18:15 ` Michal Koutný 2021-11-10 18:15 ` Michal Koutný 2021-11-10 15:20 ` Waiman Long
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