linux-kernel - Re: [PATCH RFC 5/7] sched: cfs: cpu frequency scaling arch functions

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Message-ID: <CAPtuhThe9dQkbwbXoCV0VpHohrC8UacPoL5vCn2uDqHcjbtKGA@mail.gmail.com>
Date:	Wed, 22 Oct 2014 16:20:22 -0700
From:	Mike Turquette <mturquette@...aro.org>
To:	Rik van Riel <riel@...hat.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Morten Rasmussen <Morten.Rasmussen@....com>,
	kamalesh@...ux.vnet.ibm.com, efault@....de,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Paul Turner <pjt@...gle.com>,
	Benjamin Segall <bsegall@...gle.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Patch Tracking <patches@...aro.org>,
	Tuukka Tikkanen <tuukka.tikkanen@...aro.org>,
	Amit Kucheria <amit.kucheria@...aro.org>
Subject: Re: [PATCH RFC 5/7] sched: cfs: cpu frequency scaling arch functions

On Wed, Oct 22, 2014 at 1:06 PM, Rik van Riel <riel@...hat.com> wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> On 10/22/2014 02:07 AM, Mike Turquette wrote:
>> arch_eval_cpu_freq and arch_scale_cpu_freq are added to allow the
>> scheduler to evaluate if cpu frequency should change and to invoke
>> that change from a safe context.
>>
>> They are weakly defined arch functions that do nothing by default.
>> A CPUfreq governor could use these functions to implement a
>> frequency scaling policy based on updates to per-task statistics or
>> updates to per-cpu utilization.
>>
>> As discussed at Linux Plumbers Conference 2014, the goal will be
>> to focus on a single cpu frequency scaling policy that works for
>> everyone. That may mean that the weak arch functions definitions
>> can be removed entirely and a single policy implements that logic
>> for all architectures.
>
> On virtual machines, we probably want to use both frequency and
> steal time to calculate the factor.

You mean for calculating desired cpu frequency on a virtual guest? Is
that something we want to do?

Thanks,
Mike

>
> - --
> All rights reversed
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