linux-kernel - Re: sched: deep power-saving states

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Date:	Wed, 22 Oct 2008 06:47:38 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Gregory Haskins <gregory.haskins.ml@...il.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: sched: deep power-saving states

On Wed, 22 Oct 2008 09:42:52 -0400
Gregory Haskins <gregory.haskins.ml@...il.com> wrote:

> What I was thinking is that a simple mechanism to quantify the
> power-state penalty would be to add those states as priority levels in
> the cpupri namespace.  E.g. We could substitute IDLE-RUNNING for IDLE,
> and add IDLE-PS1, IDLE-PS2, .. IDLE-PSn, OTHER, RT1, .. RT99.  This
> means the scheduler would favor waking an IDLE-RUNNING core over an
> IDLE-PS1-PSn, etc.  The question in my mind is: can the power-states
> be determined in a static fashion such that we know what value to
> quantify the idle state before we enter it?  Or is it more dynamic
> (e.g. the longer it is in an MWAIT, the deeper the sleep gets).

it's a little dynamic, but just assuming the worst will be a very good
approximation of reality. And we know what we're getting into in that
sense.

-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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