linux-kernel - Re: v2.6.26-rc7: Negative powertop values

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Message-ID: <487A212E.1080505@linux.intel.com>
Date:	Sun, 13 Jul 2008 08:37:18 -0700
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Pavel Machek <pavel@...e.cz>
CC:	Vegard Nossum <vegard.nossum@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: v2.6.26-rc7: Negative powertop values

Pavel Machek wrote:
> On Tue 2008-07-08 06:52:51, Arjan van de Ven wrote:
>> On Sun, 6 Jul 2008 21:48:45 +0200
>> Pavel Machek <pavel@...e.cz> wrote:
>>
>>>> [I assume you know that doing a software unplug you burn more power
>>>> than by leaving the cpu idle]
>>> We should really fix that one day...
>> yeah but it's incredibly hard to get right (in the light of the bios
>> constantly changing what our allowed C-states are)... and the best case
> 
> What can happen there? So BIOS decides C4 may no longer be cool idea
> because we have AC power now, but that does not mean C4 stops working,
> right?

it's also the other way around; you put the sleepy core in C4 because C6 is not available;
then C6 becomes available and the sleepy core is wasting power;

Either way, the *best* case you get is to be equal to being idle.....

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