linux-kernel - Re: [PATCH v3 1/1] cgroup: make per-cgroup pressure stall tracking configurable

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Message-ID: <YKz07nx3E8UEo1xa@cmpxchg.org>
Date:   Tue, 25 May 2021 09:00:30 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     tj@...nel.org, lizefan.x@...edance.com, mingo@...hat.com,
        peterz@...radead.org, shakeelb@...gle.com, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        minchan@...nel.org, corbet@....net, bristot@...hat.com,
        paulmck@...nel.org, rdunlap@...radead.org,
        akpm@...ux-foundation.org, tglx@...utronix.de, macro@...am.me.uk,
        viresh.kumar@...aro.org, mike.kravetz@...cle.com,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        cgroups@...r.kernel.org, kernel-team@...roid.com
Subject: Re: [PATCH v3 1/1] cgroup: make per-cgroup pressure stall tracking
 configurable

On Mon, May 24, 2021 at 12:53:39PM -0700, Suren Baghdasaryan wrote:
> PSI accounts stalls for each cgroup separately and aggregates it at each
> level of the hierarchy. This causes additional overhead with psi_avgs_work
> being called for each cgroup in the hierarchy. psi_avgs_work has been
> highly optimized, however on systems with large number of cgroups the
> overhead becomes noticeable.
> Systems which use PSI only at the system level could avoid this overhead
> if PSI can be configured to skip per-cgroup stall accounting.
> Add "cgroup_disable=pressure" kernel command-line option to allow
> requesting system-wide only pressure stall accounting. When set, it
> keeps system-wide accounting under /proc/pressure/ but skips accounting
> for individual cgroups and does not expose PSI nodes in cgroup hierarchy.
> 
> Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>

Acked-by: Johannes Weiner <hannes@...xchg.org>