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From:   Vincent Guittot <vincent.guittot@linaro.org>
Date:   Wed, 18 May 2022 14:03:31 +0200
Message-ID: <CAKfTPtBAkQpKtZMC5uV6hNeMqe9rJHd_GLHVFf2o3r=HvqH9fg@mail.gmail.com>
Subject: Re: [External] Re: [RFC PATCH] sched: Enable root level cgroup
 bandwidth control
To:     "Feiran Zheng ." <fam.zheng@bytedance.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        linux-kernel@vger.kernel.org, Steven Rostedt <rostedt@goodmis.org>,
        Ben Segall <bsegall@google.com>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        zhouchengming@bytedance.com, fam@euphon.net,
        Mel Gorman <mgorman@suse.de>, Ingo Molnar <mingo@redhat.com>,
        songmuchun@bytedance.com, Juri Lelli <juri.lelli@redhat.com>
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On Wed, 18 May 2022 at 12:38, Feiran Zheng . <fam.zheng@bytedance.com> wrote:
>
> On Wed, May 18, 2022 at 11:21 AM Peter Zijlstra <peterz@infradead.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.

This looks like thermal or power budget management. We have other ways
to do so with powercap or idle injection. Did you consider those
solutions ?