linux-kernel - Re: [PATCH 1/3] Added runqueue clock normalized with cpufreq

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Message-ID: <1292599007.2266.290.camel@twins>
Date:	Fri, 17 Dec 2010 16:16:47 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Harald Gustafsson <hgu1972@...il.com>
Cc:	Harald Gustafsson <harald.gustafsson@...csson.com>,
	Dario Faggioli <faggioli@...dalf.sssup.it>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Claudio Scordino <claudio@...dence.eu.com>,
	Michael Trimarchi <trimarchi@...is.sssup.it>,
	Fabio Checconi <fabio@...dalf.sssup.it>,
	Tommaso Cucinotta <cucinotta@...up.it>,
	Juri Lelli <juri.lelli@...il.com>,
	Dario Faggioli <raistlin@...ux.it>
Subject: Re: [PATCH 1/3] Added runqueue clock normalized with cpufreq

On Fri, 2010-12-17 at 16:06 +0100, Harald Gustafsson wrote:
> 2010/12/17 Peter Zijlstra <peterz@...radead.org>:
> > This is all assuming lowering the frequency is sensible to begin with in
> > the first place... but that's all part of the CPUfreq governor, it needs
> > to find a way to lower energy usage while conforming to the system
> > constraints.
> 
> Yes, I and you have already suggested the safe way to not lower it below
> the total dl bandwidth. But for softer use cases it might be possible to
> e.g. exclude threads with longer periods than cpufreq change periods in the
> minimum frequency.

I was more hinting at the fact that CPUfreq is at best a controversial
approach to power savings. I much prefer the whole race-to-idle
approach, its much simpler.
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