linux-kernel - Re: [PATCH cgroup/for-4.15] cgroup, sched: Move basic cpu stats from cgroup.stat to cpu.stat

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Date:   Tue, 24 Oct 2017 10:35:04 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Tejun Heo <tj@...nel.org>
Cc:     Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Ingo Molnar <mingo@...hat.com>, Roman Gushchin <guro@...com>,
        linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        kernel-team@...com
Subject: Re: [PATCH cgroup/for-4.15] cgroup, sched: Move basic cpu stats from
 cgroup.stat to cpu.stat

On Mon, Oct 23, 2017 at 04:18:27PM -0700, Tejun Heo wrote:
> The basic cpu stat is currently shown with "cpu." prefix in
> cgroup.stat, and the same information is duplicated in cpu.stat when
> cpu controller is enabled.  This is ugly and not very scalable as we
> want to expand the coverage of stat information which is always
> available.
> 
> This patch makes cgroup core always create "cpu.stat" file and show
> the basic cpu stat there and calls the cpu controller to show the
> extra stats when enabled.  This ensures that the same information
> isn't presented in multiple places and makes future expansion of basic
> stats easier.
> 
> Signed-off-by: Tejun Heo <tj@...nel.org>
> ---
> Hello,
> 
> The more I think about showing cpu stat in cgroup.stat, the uglier it
> seems. 

I've not been paying much attention to this, could you elaborate on the
problems there?

> This patch flips it so that "cpu.stat" is always available
> with basic cpu stat instead.  It only changes the presentation and
> changes to the scheduler code is minimal.  Will route with the other
> cpu controller changes through cgroup/for-4.15 unless there are
> objections.

And this is -v2 only? I'm a little lost on how all that connects.