Re: sched: deep power-saving states

From: Gregory Haskins
Date: Wed Oct 22 2008 - 10:01:24 EST

Arjan van de Ven wrote:
> On Wed, 22 Oct 2008 09:42:52 -0400
> Gregory Haskins <> 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.

Ok, but if we just assume the worst case always, how do I differentiate
between, say, IDLE-RUNNING and IDLE-PSn? If I assign them all to
IDLE-PSn apriori its no better than the basic single IDLE state we
support today. Or am I misunderstanding you?


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