linux-kernel - Re: [PATCH] cpuidle: menu governor: reduce latency on exit

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Message-ID: <4e5e476b0907240841y183a4c08r3abf3d4fb7489284@mail.gmail.com>
Date:	Fri, 24 Jul 2009 17:41:26 +0200
From:	Corrado Zoccolo <czoccolo@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	venkatesh.pallipadi@...el.com, abelay@...ell.com,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpuidle: menu governor: reduce latency on exit

Hi Andrew,
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.

Corrado

On Fri, Jul 24, 2009 at 12:05 AM, Andrew
Morton<akpm@...ux-foundation.org> wrote:
> On Sun, 19 Jul 2009 16:59:46 +0200
> Corrado Zoccolo <czoccolo@...il.com> wrote:
>
>> This patch moves 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.
>>
>
> Was there any observed and/or measured effect as a result of this patch?
>
> If so, please send a description of that effect, thanks.
>
>



-- 
__________________________________________________________________________

dott. Corrado Zoccolo                          mailto:czoccolo@...il.com
PhD - Department of Computer Science - University of Pisa, Italy
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