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Date:   Fri, 10 May 2019 14:16:59 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Dan Schatzberg <dschatzberg@fb.com>
Cc:     Tejun Heo <tj@kernel.org>, Li Zefan <lizefan@huawei.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        <linux-kernel@vger.kernel.org>, <cgroups@vger.kernel.org>
Subject: Re: [PATCH] psi: Expose pressure metrics on root cgroup
Message-Id: <20190510141659.08f58679c2eb3d321092dc23@linux-foundation.org>
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On Fri, 10 May 2019 10:49:34 -0700 Dan Schatzberg <dschatzberg@fb.com> wrote:

> Pressure metrics are already recorded and exposed in procfs for the
> entire system, but any tool which monitors cgroup pressure has to
> special case the root cgroup to read from procfs. This patch exposes
> the already recorded pressure metrics on the root cgroup.
> 

Documentation/admin-guide/cgroup-v2.rst says "A read-only nested-key
file which exists on non-root cgroups". 
Documentation/accounting/psi.txt could do woth some clarification as
well.