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

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Date:	Fri, 17 Dec 2010 20:16:42 +0100
From:	Dario Faggioli <raistlin@...ux.it>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Harald Gustafsson <harald.gustafsson@...csson.com>,
	Harald Gustafsson <hgu1972@...il.com>,
	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>
Subject: Re: [PATCH 1/3] Added runqueue clock normalized with cpufreq

On Fri, 2010-12-17 at 19:59 +0100, Peter Zijlstra wrote: 
> > However, converting the basic mechanism into a CPUfreq governor should
> > be easily doable... The only problem is finding the time for that! ;-P 
> 
> Ah, I think Harald will solve that for you,.. :)
> 
Yeah, I saw that... Help is a wonderful thing, you know? :-P

> > And, at least for the meantime, this seems a very very nice solution.
> > The only thing I don't like is that division which would end up in being
> > performed at each tick/update_curr_dl(), but we can try to find out a
> > way to mitigate this, what do you think Harald?
> 
> A simple mult and shift-right should do. You can either pre-compute for
> a platform, or compute the inv multiplier in the cpufreq notifier thing.
>
Yeah, I was thinking about something like the last solution you just
propose, but we'll consider all of them.

Thanks and Regards,
Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
----------------------------------------------------------------------
Dario Faggioli, ReTiS Lab, Scuola Superiore Sant'Anna, Pisa  (Italy)

http://retis.sssup.it/people/faggioli -- dario.faggioli@...ber.org

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