linux-kernel - Re: Strange C3/C4 sleep state behaviour

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Date:	Fri, 16 May 2008 00:18:03 +0200
From:	Björn Steinbrink <B.Steinbrink@....de>
To:	Pascal Brückner <pascal_2001@....de>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Strange C3/C4 sleep state behaviour

On 2008.05.15 23:11:00 +0200, Pascal Brückner wrote:
> Hello!
>
> I'm recompiling my kernel recently to optimize the power usage of my
> laptop (IBM ThinkPad X31). So far, my most efficient kernel at the
> moment is a self-compiled 2.6.22 with phc patches for undervolting,
> suspend2/tuxonice and hrtimers patches to force HPET on my ICH4-M chipset.
>
> Because everyone says, that newer kernel revisions are much more energy
> efficient than my 2.6.22, i tried to compile one to reach at least the
> energy usage of my recent kernel.
> Sadly, this doesn't work because of only one issue:
> With activated wireless networking (atheros chipset with recent madwifi
> driver) i'm losing much energy due to the fact, that my cpu is
> significant more in C2 state than in C3/C4.

Do you have CONFIG_CPU_IDLE enabled? That made a huge difference for me.
Before that was available, _disabling_ CONFIG_NO_HZ also helped when
wifi was enabled (but IIRC made things worse with wifi disabled).

Björn
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