linux-kernel - Re: [PATCH] psi: Add PSI_CPU

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Message-ID: <YCGAYEiyTKCO71E3@cmpxchg.org>
Date:   Mon, 8 Feb 2021 13:18:08 -0500
From:   Johannes Weiner <hannes@...xchg.org>
To:     Chengming Zhou <zhouchengming@...edance.com>
Cc:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, rostedt@...dmis.org,
        dietmar.eggemann@....com, linux-kernel@...r.kernel.org,
        songmuchun@...edance.com
Subject: Re: [PATCH] psi: Add PSI_CPU_FULL state

On Sun, Feb 07, 2021 at 03:24:02PM +0800, Chengming Zhou wrote:
> The FULL state doesn't exist for the CPU resource at the system level,
> but exist at the cgroup level, means all non-idle tasks in a cgroup are
> delayed on the CPU resource which used by others outside of the cgroup.
> 
> Co-developed-by: Muchun Song <songmuchun@...edance.com>
> Signed-off-by: Muchun Song <songmuchun@...edance.com>
> Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>

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

That metric's come up in our production environment recently as well,
it makes a lot of sense.

In addition to outside competition, this also applies to downtimes
enforced by cpu.max - another cgroup usecase that is worth mentioning
in the changelog & code comment.

Thanks