linux-kernel - Re: [PATCH v2] cpuidle: Fix the menu governor to boost IO performance

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Date:	Thu, 17 Sep 2009 15:39:12 +0200
From:	Arjan van de Ven <arjan@...radead.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, lenb@...nel.org, mingo@...e.hu,
	yanmin_zhang@...ux.intel.com, jens.axboe@...cle.com,
	ink@...assic.park.msu.ru, Corrado Zoccolo <czoccolo@...il.com>
Subject: Re: [PATCH v2] cpuidle: Fix the menu governor to boost IO
 performance

On Tue, 15 Sep 2009 16:23:06 -0700
Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Tue, 15 Sep 2009 05:42:59 +0200
> Arjan van de Ven <arjan@...radead.org> wrote:
> 
> > Fix the menu idle governor which balances power savings, energy
> > efficiency and performance impact.
> 
> This patch clashes a bit with
> cpuidle-menu-governor-reduce-latency-on-exit.patch (which was sent to
> the ACPI maintainers a month ago and ignored).
> 
> <im-fed-up-with-this-crap-ill-just-merge-it-and-if-it-breaks-dont-blame-me>
> 
> 
> I restaged cpuidle-menu-governor-reduce-latency-on-exit.patch so it
> goes after
> cpuidle-fix-the-menu-governor-to-boost-io-performance.patch. perhaps
> you could take a look at Corrado's change?
> 
>  
> 
> From: Corrado Zoccolo <czoccolo@...il.com>
> 
> Move the state residency accounting and statistics computation off
> the hot exit path.
> 
> On exit, the need to recompute statistics is recorded, and new
> statistics will be computed when menu_select is called again.
> 
> The expected effect is to reduce processor wakeup latency from sleep
> (C-states).  We are speaking of few hundreds of cycles reduction out
> of a several microseconds latency (determined by the hardware
> transition), so it is difficult to measure.
> 
> Signed-off-by: Corrado Zoccolo <czoccolo@...il.com>
> Cc: Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>
> Cc: Len Brown <len.brown@...el.com>
> Cc: Adam Belay <abelay@...ell.com
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>

I checked the last residency thing... and it's fine

Acked-by: Arjan van de Ven <arjan@...ux.intel.com>



-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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