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From:   Vincent Guittot <vincent.guittot@linaro.org>
Date:   Wed, 18 May 2022 16:31:38 +0200
Message-ID: <CAKfTPtA4qRUpMK4gw0STFg3kQqhpxCJpOMy9HgbSKaeVwfSjEQ@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>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Cristian Marussi <cristian.marussi@arm.com>
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Precedence: bulk

Adding daniel and cristian who works on some powercap implementation

On Wed, 18 May 2022 at 14:56, Feiran Zheng . <fam.zheng@bytedance.com> wrote:
>
> On Wed, May 18, 2022 at 1:03 PM Vincent Guittot
> <vincent.guittot@linaro.org> wrote:
> >
> > 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 ?
>
> Hi Vincent,
>
> I looked at powercap, and it seems Intel only? Any idea about AMD/ARM?
> There seems nothing for them under drivers/powercap/.

there is a DTPM powercap provider in the latest kernel and a scmi
power capp provider is under review
>
> I don't know the idle injection interface, can you please give more hints?

idle injection can be used with cpuidle cooling device and there were
some discussion to make a dtpm idle injection device but I think this
has  never been sent on mailing list


>
> I also plan to test uclamp, still need to learn more about that.
>
> Fam