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

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Date:	Wed, 22 Oct 2014 16:06:48 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Mike Turquette <mturquette@...aro.org>, peterz@...radead.org,
	mingo@...nel.org
CC:	linux-kernel@...r.kernel.org, preeti@...ux.vnet.ibm.com,
	Morten.Rasmussen@....com, kamalesh@...ux.vnet.ibm.com,
	efault@....de, nicolas.pitre@...aro.org,
	linaro-kernel@...ts.linaro.org, daniel.lezcano@...aro.org,
	dietmar.eggemann@....com, pjt@...gle.com, bsegall@...gle.com,
	vincent.guittot@...aro.org, patches@...aro.org,
	tuukka.tikkanen@...aro.org, amit.kucheria@...aro.org
Subject: Re: [PATCH RFC 5/7] sched: cfs: cpu frequency scaling arch functions

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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.

- -- 
All rights reversed
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