linux-kernel - RE: [linux-pm] [RFC-PATCH] Improve Menu Governor Prediction of interrupted C states.

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Date:	Wed, 6 Aug 2008 09:51:14 +0800
From:	"Wei, Gang" <gang.wei@...el.com>
To:	"Woodruff, Richard" <r-woodruff2@...com>,
	"Linux Power Management List" <linux-pm@...ts.osdl.org>
Cc:	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: RE: [linux-pm] [RFC-PATCH] Improve Menu Governor Prediction of interrupted C states.

> Hi,
> 
>> I also found current cpuidle Menu governor should have some problems
>> while predicting next non-expected break-event after some expected
>> break-events. The measured_us/elapsed_us/predicted_us will become
larger
>> and larger once (measured_us + BREAK_FUZZ >= data->expected_us -
>> target->exit_latency). The major point is that it should be
>> last_residency, not measured_us, that need to be used to do comparing
>> and distinguish between expected & non-expected events.
>> 
>> Below is my draft patch (not tested) for this. It is simple and
should
>> also be effective for high interrupt rates case.
> 
> This does seem to give better guesses.  However, first tests are not
showing
> as well as the irq time stamp version I posted. 
> 
> I'll need to grab some hardware trace to see what is going on.

Thanks for the trial. My original patch has already been merged into
another patch "[patch 2/3] cpuidle: Menu governor fix wrong usage of
measured_us" sent out by Venkatesh. The new patch should be more intact.

Jimmy
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