linux-kernel - Re: [PATCH v3] sched/core: add forced idle accounting for cgroups

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Message-ID: <CABk29NvMRWbJgZ7VdzdeDVz0v=PKJJJ0gFk=+X884U25ZJhbsA@mail.gmail.com>
Date:   Mon, 27 Jun 2022 15:35:21 -0700
From:   Josh Don <joshdon@...gle.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Cruz Zhao <CruzZhao@...ux.alibaba.com>
Subject: Re: [PATCH v3] sched/core: add forced idle accounting for cgroups

Thanks Tejun,

On Mon, Jun 27, 2022 at 2:16 AM Tejun Heo <tj@...nel.org> wrote:
>
> Hello,
>
> On Tue, Jun 21, 2022 at 04:44:43PM -0700, Josh Don wrote:
> > 4feee7d1260 previously added per-task forced idle accounting. This patch
> > extends this to also include cgroups.
> >
> > rstat is used for cgroup accounting, except for the root, which uses
> > kcpustat in order to bypass the need for doing an rstat flush when
> > reading root stats.
> >
> > Only cgroup v2 is supported. Similar to the task accounting, the cgroup
> > accounting requires that schedstats is enabled.
>
> Generally looks fine from cgroup side. One nitpick follow.
>
> > +     seq_printf(seq, "forceidle_usec %llu\n", forceidle_time);
>
> Would it make sense to namespace the name to reflect the fact that
> this is tied to core scheduling? e.g. something like
> core.force_idle_usec (and yeah, underscore between words, please). I
> kinda hate that the feature is named "core". The word is so
> overloaded.

Sure, although a namespace of "core_sched" would be a bit clearer,
since as you point out "core" is pretty overloaded :)

Lack of underscore for forceidle was to be consistent with
"core_forceidle_sum" being dumped from /proc/pid/sched, but I'm fine
with it either way.

So,

core_sched.force_idle_usec ?

>
> Thanks.
>
> --
> tejun