linux-kernel - Re: [PATCH 3/3] cgroup: no need for cgroup

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Date:   Mon, 25 Oct 2021 07:27:02 -1000
From:   Tejun Heo <tj@...nel.org>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Michal Koutný <mkoutny@...e.com>,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] cgroup: no need for cgroup_mutex for /proc/cgroups

On Sun, Oct 24, 2021 at 11:19:16PM -0700, Shakeel Butt wrote:
> On the real systems, the cgroups hierarchies are setup early and just
> once by the node controller, so, other than number of cgroups, all
> information in /proc/cgroups remain same for the system uptime. Let's
> remove the cgroup_mutex usage on reading /proc/cgroups. There is a
> chance of inconsistent number of cgroups for co-mounted cgroups while
> printing the information from /proc/cgroups but that is not a big
> issue. In addition /proc/cgroups is a v1 specific interface, so the
> dependency on it should reduce over time.
> 
> The main motivation for removing the cgroup_mutex from /proc/cgroups is
> to reduce the avenues of its contention. On our fleet, we have observed
> buggy application hammering on /proc/cgroups and drastically slowing
> down the node controller on the system which have many negative
> consequences on other workloads running on the system.
> 
> Signed-off-by: Shakeel Butt <shakeelb@...gle.com>

Applied 1-3 to cgroup/for-5.16.

Thanks.

-- 
tejun