Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Mon, 8 Feb 2021 13:18:08 -0500
From:   Johannes Weiner <hannes@cmpxchg.org>
To:     Chengming Zhou <zhouchengming@bytedance.com>
Cc:     mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
        vincent.guittot@linaro.org, rostedt@goodmis.org,
        dietmar.eggemann@arm.com, linux-kernel@vger.kernel.org,
        songmuchun@bytedance.com
Subject: Re: [PATCH] psi: Add PSI_CPU_FULL state
Message-ID: <YCGAYEiyTKCO71E3@cmpxchg.org>
References: <20210207072402.67532-1-zhouchengming@bytedance.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20210207072402.67532-1-zhouchengming@bytedance.com>
Precedence: bulk

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@bytedance.com>
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>

Acked-by: Johannes Weiner <hannes@cmpxchg.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