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Date:   Tue, 25 May 2021 09:12:59 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Suren Baghdasaryan <surenb@google.com>
Cc:     tj@kernel.org, hannes@cmpxchg.org, lizefan.x@bytedance.com,
        mingo@redhat.com, shakeelb@google.com, juri.lelli@redhat.com,
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        minchan@kernel.org, corbet@lwn.net, bristot@redhat.com,
        paulmck@kernel.org, rdunlap@infradead.org,
        akpm@linux-foundation.org, tglx@linutronix.de, macro@orcam.me.uk,
        viresh.kumar@linaro.org, mike.kravetz@oracle.com,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        cgroups@vger.kernel.org, kernel-team@android.com
Subject: Re: [PATCH v3 1/1] cgroup: make per-cgroup pressure stall tracking
 configurable
Message-ID: <YKyje/yNnwVyTcDB@hirez.programming.kicks-ass.net>
References: <20210524195339.1233449-1-surenb@google.com>
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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@google.com>

>  kernel/sched/psi.c                            | 30 +++++++-----

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>