linux-kernel - Re: [PATCH 0/6] cpufreq: Add sampling window to enhance ondemand governor power efficiency

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Message-ID: <20101223205148.GB6441@comet.dominikbrodowski.net>
Date:	Thu, 23 Dec 2010 21:51:48 +0100
From:	Dominik Brodowski <linux@...inikbrodowski.net>
To:	Dave Jones <davej@...hat.com>,
	Youquan Song <youquan.song@...el.com>, cpufreq@...r.kernel.org,
	venki@...gle.com, arjan@...ux.intel.com, lenb@...nel.org,
	suresh.b.siddha@...el.com, kent.liu@...el.com,
	chaohong.guo@...el.com, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org,
	Youquan Song <youquan.song@...ux.intel.com>
Subject: Re: [PATCH 0/6] cpufreq: Add sampling window to enhance ondemand
 governor power efficiency

Hey,

On Thu, Dec 23, 2010 at 12:34:02PM -0500, Dave Jones wrote:
> On Thu, Dec 23, 2010 at 12:00:20PM +0100, Dominik Brodowski wrote:
>  > Interesting approach, but seems to be quite different from what "ondemand"
>  > does at the moment. And, as David Niemi pointed out, it seems to be more
>  > Intel-specific. Therefore, what do you think about adding this different
>  > algorithm as a different governor, and keep the "ondemand" algorithm more or
>  > less as it is?
> 
> I'm hesitant to merge more governors. (We already have too many imo).

AFAICS, we do have two in-kernel dynamic frequency scaling governors, one of
which doesn't seem to get much usage (conservative)...

> The userspace logic for automatically deciding which is the best one to use is
> already pretty hairy, so any additional ones at this point would have to be
> accompanied with some really compelling reasons why the existing ones can't
> be fixed in an acceptable manner.

Well, if the underlying alogrithm is fundamentally different -- such as when
looking at sampling windows instead of the past one window -- this seems to
be a "compelling" reason to me. Especially if one governor works well on
certain platforms, and the other one works better on other platforms.

Best,
	Dominik
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