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From: Tejun Heo <tj@kernel.org>
To: "Michal Koutný" <mkoutny@suse.com>
Cc: Waiman Long <longman@redhat.com>, Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Valentin Schneider <vschneid@redhat.com>,
	Zefan Li <lizefan.x@bytedance.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	cgroups@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] cgroup: Skip subtree root in cgroup_update_dfl_csses()
Date: Thu, 28 Jul 2022 07:26:05 -1000	[thread overview]
Message-ID: <YuLGrXyXj6a2yigJ@slm.duckdns.org> (raw)
In-Reply-To: <20220728144426.GA26631@blackbody.suse.cz>

On Thu, Jul 28, 2022 at 04:44:26PM +0200, Michal Koutný wrote:
> On Wed, Jul 27, 2022 at 08:58:15PM -0400, Waiman Long <longman@redhat.com> wrote:
> > The cgroup_update_dfl_csses() function updates css associations when a
> > cgroup's subtree_control file is modified. Any changes made to a cgroup's
> > subtree_control file, however, will only affect its descendants but not
> > the cgroup itself. 
> 
> I find this correct.
> 
> > So there is no point in migrating csses associated with that cgroup.
> > We can skip them instead.
> 
> Alone it's not such a big win but it componds with the recent Tejun's
> threadgroup_rwsem elision.

The chance is that if you're writing to a cgroup's subtree_control, that
cgroup is gonna be empty. The only case I can think of that this would make
a difference is w/ threaded cgroups, but it does make sense.

Thanks.

-- 
tejun

  parent reply	other threads:[~2022-07-28 17:26 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-28  0:58 [PATCH 1/2] cgroup/cpuset: Keep current cpus list if cpus affinity was explicitly set Waiman Long
2022-07-28  0:58 ` [PATCH 2/2] cgroup: Skip subtree root in cgroup_update_dfl_csses() Waiman Long
2022-07-28 14:44   ` Michal Koutný
2022-07-28 14:49     ` Waiman Long
2022-07-28 17:26     ` Tejun Heo [this message]
2022-07-28 17:27   ` Tejun Heo
2022-07-28 14:44 ` [PATCH 1/2] cgroup/cpuset: Keep current cpus list if cpus affinity was explicitly set Michal Koutný
2022-07-28 14:59   ` Waiman Long
2022-07-28 15:23     ` Michal Koutný
2022-07-28 15:35       ` Waiman Long
2022-07-28 16:50     ` Valentin Schneider
2022-07-28 17:42       ` Waiman Long
2022-07-28 17:23 ` Tejun Heo
2022-07-28 18:57   ` Waiman Long
2022-07-28 19:02     ` Tejun Heo
2022-07-28 19:21       ` Waiman Long
2022-07-28 20:44         ` Tejun Heo
2022-07-28 21:04           ` Waiman Long
2022-07-28 21:39             ` Tejun Heo
2022-07-29 14:15               ` Valentin Schneider
2022-07-29 14:50                 ` Waiman Long
2022-07-29 18:31                   ` Waiman Long

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