linux-kernel - Re: cpufreq doesn't seem to work in Intel Q9300

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Message-ID: <20080811193316.GA16631@isilmar.linta.de>
Date:	Mon, 11 Aug 2008 21:33:17 +0200
From:	Dominik Brodowski <linux@...inikbrodowski.net>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Adrian Bunk <bunk@...nel.org>, S K <nospamnoham@...il.com>,
	Zhao Yakui <yakui.zhao@...el.com>,
	Thomas Renninger <trenn@...e.de>,
	Alan Jenkins <alan-jenkins@...fmail.co.uk>,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: cpufreq doesn't seem to work in Intel Q9300

Hi,

On Mon, Aug 11, 2008 at 07:11:28AM -0700, Arjan van de Ven wrote:
> 1) when the cpu is idle (as in "idle loop C states/hlt"; p4_clockmod
> doesn't mean anything.. the clock is stopped not just skipped.
> 2) when the cpu is executing code (eg non-idle), it takes more power
> for a unit of time than it takes when it's idle

This statement might be true, but might also be wrong:
	a) on systems where only C1 is exported, p4-clockmod most often
	   equals the state the CPU is in when in C1[*], so we're in a 
	   win-win, or lose-lose situation.
	b) IIRC 50% throttling is not "execute-one-statement
	   skip-one-statement execute-one-statement, etc." but instead
	   work for N us, skip for N us, work for N us, etc. Therefore,
	   the situation is a bit more compilcated.

Still, I agree that p4-clockmod is useful mostly in corner cases (and for
developing the cpufreq infrastructure in the first case, but that's another
story)

[*] or C2 even?

Best,
	Dominik
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