linux-kernel - Re: [PATCH-cgroup 1/2] cgroup: Show # of subsystem CSSes in /proc/cgroups

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Message-ID: <Zowzvf2NEOzgXYr3@slm.duckdns.org>
Date: Mon, 8 Jul 2024 08:45:17 -1000
From: Tejun Heo <tj@...nel.org>
To: Waiman Long <longman@...hat.com>
Cc: Zefan Li <lizefan.x@...edance.com>,
	Johannes Weiner <hannes@...xchg.org>, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH-cgroup 1/2] cgroup: Show # of subsystem CSSes in
 /proc/cgroups

Hello, Waiman.

On Fri, Jul 05, 2024 at 08:56:21PM -0400, Waiman Long wrote:
> The /proc/cgroups file shows the number of cgroups for each of the
> subsystems.  With cgroup v1, the number of CSSes is the same as the
> number of cgroups. That is not the case anymore with cgroup v2. The
> /proc/cgroups file cannot show the actual number of CSSes for the
> subsystems that are bound to cgroup v2.
> 
> So if a v2 cgroup subsystem is leaking cgroups (typically memory
> cgroup), we can't tell by looking at /proc/cgroups which cgroup
> subsystems may be responsible.  This patch adds a css counter in the
> cgroup_subsys structure to keep track of the number of CSSes for each
> of the cgroup subsystems.

The count sounds useful to me but can we add it in cgroup.stats instead?

Thanks.

-- 
tejun