linux-kernel - Re: [Bug #12152] Huge wakeups number from i1915

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Date:	Mon, 08 Dec 2008 07:24:08 +0100
From:	Yves-Alexis Perez <corsac@...ian.org>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>
Subject: Re: [Bug #12152] Huge wakeups number from i1915

On dim, 2008-12-07 at 15:12 -0800, Arjan van de Ven wrote:
> 
> > > at least in some of the cases where this has been seen the cause
> is
> > > the following:
> > > The i915 DRM driver used to do polling for completion, busy
> > > waiting. It moved to be interrupt driven, which is usually better
> > > for power, but it will show up as more wakeups in powertop....
> > 
> > IOW, this is not a regression?
> 
> I don't know about this specifc case (not enough information) but for
> the case I described it's not a regression. Going to interrupt driven
> from busy waiting is an improvement not a regression :)

Well, several thousand or more interrupts really seems like a
regression :). But it seems that's the same thing as the “IRQ
spinning” (there was a thread on dri-devel about that).

It seems fixed with a patch from Matthew Garrett applied to
drm-intel/for-airlied but I don't think this has been applied to Linus
master.

Cheers,
-- 
Yves-Alexis

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