linux-kernel - Re: [External] Re: [RFC PATCH] sched: Enable root level cgroup bandwidth control

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Date:   Wed, 18 May 2022 11:38:02 +0100
From:   "Feiran Zheng ." <fam.zheng@...edance.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        zhouchengming@...edance.com,
        Vincent Guittot <vincent.guittot@...aro.org>, fam@...hon.net,
        Mel Gorman <mgorman@...e.de>, Ingo Molnar <mingo@...hat.com>,
        songmuchun@...edance.com, Juri Lelli <juri.lelli@...hat.com>
Subject: Re: [External] Re: [RFC PATCH] sched: Enable root level cgroup
 bandwidth control

On Wed, May 18, 2022 at 11:21 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Wed, May 18, 2022 at 11:08:41AM +0100, Fam Zheng wrote:
> > In the data center there sometimes comes a need to throttle down a
> > server,
>
> Why?

For economical reasons there can be over-provisioning in DC power
supply (UPS capacity etc) because the utilization expectation of the
racks is not maximum value. But the workload can be client driven,
depending on how many users are online, and in the end the power
supply may overload and trip itself. To avoid that, upon a threshold,
some servers need to be brought down or throttled. The latter is
obviously going to be much more smooth.