linux-kernel - Re: [PATCH] cgroup: Make cgroup_rstat_updated() ready for root cgroup usage

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Message-ID: <20180426213627.GX1911913@devbig577.frc2.facebook.com>
Date:   Thu, 26 Apr 2018 14:36:27 -0700
From:   Tejun Heo <tj@...nel.org>
To:     lizefan@...wei.com, hannes@...xchg.org
Cc:     cgroups@...r.kernel.org, linux-kernel@...r.kernel.org, guro@...com,
        kernel-team@...com
Subject: Re: [PATCH] cgroup: Make cgroup_rstat_updated() ready for root
 cgroup usage

On Mon, Apr 02, 2018 at 02:49:13PM -0700, Tejun Heo wrote:
> From b7be022bf811d02605098fa61b7545bc146b78e7 Mon Sep 17 00:00:00 2001
> From: Tejun Heo <tj@...nel.org>
> Date: Mon, 2 Apr 2018 14:45:20 -0700
> 
> cgroup_rstat_updated() ensures that the cgroup's rstat is linked to
> the parent.  If there's no parent, it never gets linked and the
> function ends up grabbing and releasing the cgroup_rstat_lock each
> time for no reason which can be expensive.
> 
> This hasn't been a problem till now because nobody was calling the
> function for the root cgroup but rstat is gonna be exposed to
> controllers and use cases, so let's get ready.  Make
> cgroup_rstat_updated() an no-op for the root cgroup.
> 
> Signed-off-by: Tejun Heo <tj@...nel.org>

Applied to cgroup/for-4.18.

Thanks.

-- 
tejun