linux-kernel - Re: [PATCH 09/12] irq: implement IRQ expecting

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Message-ID: <alpine.LFD.2.00.1006181144390.4290@localhost.localdomain>
Date:	Fri, 18 Jun 2010 11:45:16 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Tejun Heo <tj@...nel.org>
cc:	Arjan van de Ven <arjan@...radead.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>, mingo@...e.hu,
	bphilips@...e.de, yinghai@...nel.org, akpm@...ux-foundation.org,
	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
	jeff@...zik.org, linux-ide@...r.kernel.org,
	stern@...land.harvard.edu, gregkh@...e.de, khali@...ux-fr.org
Subject: Re: [PATCH 09/12] irq: implement IRQ expecting

On Fri, 18 Jun 2010, Tejun Heo wrote:
> Hello,
> 
> On 06/18/2010 08:26 AM, Arjan van de Ven wrote:
> > On Thu, 17 Jun 2010 18:47:19 +0200
> > Tejun Heo <tj@...nel.org> wrote:
> > 
> >>
> >> Hmmm... the thing is that there will be many cases which won't fit
> >> irq_expect() model (why irq_watch() exists in the first place) and for
> >> the time being libata is the only one providing that data.  Would the
> >> data still be useful to determine which c-state to use?
> > 
> > yes absolutely. One of the hard cases right now that the C state code
> > has is that it needs to predict the future. While it has a ton of
> > heuristics, including some is there IO oustanding" ones, libata is a
> > really good case: libata will know generally that within one seek time
> > (5 msec on rotating rust, much less on floating electrons) there'll be
> > an interrupt (give or take, but this is what we can do heuristics for
> > on a per irq level).
> > So it's a good suggestion of what the future will be like, MUCH better
> > than any hint we have right now... all we have right now is some
> > history, and when the next timer is.... 
> 
> Cool, good to know.  It shouldn't be difficult to at all to add.  Once
> the whole thing gets generally agreed on, I'll work on that.
> 
> Thomas, Ingo, through which tree should these patches routed through?

I'm going to pull that into tip/genirq I guess

Thanks,

	tglx
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