linux-kernel - Re: [patch 00/22] high resolution timers / dynamic ticks

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Date:	Thu, 05 Oct 2006 23:11:56 +0200
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andi Kleen <ak@...e.de>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	John Stultz <johnstul@...ibm.com>,
	Valdis Kletnieks <valdis.kletnieks@...edu>,
	Arjan van de Ven <arjan@...radead.org>,
	Dave Jones <davej@...hat.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Jim Gettys <jg@...top.org>,
	Roman Zippel <zippel@...ux-m68k.org>, akpm@...l.org
Subject: Re: [patch 00/22] high resolution timers / dynamic ticks - V3

On Thu, 2006-10-05 at 22:57 +0200, Andi Kleen wrote:
> > ah, that's still the VAIO, right? Do you get a 'slow' LOC count on 
> > /proc/interrupts even on a stock kernel? If yes then that's a 
> > fundamentally sick local APIC timer interrupt. Stock kernel should show 
> > sickness too, if for example you boot an SMP kernel on it - can you 
> > confirm that? (the UP-IOAPIC only relies for profiling on the lapic 
> > timer, so there the only sickness you should see on the stock kernel is 
> > a non-working readprofile)
> 
> When I was hacking on my old noidletick patch I ran into this
> problem on several machines too.
> 
> But usually the problem wasn't that it was too slow, but that
> it completely stopped in C2 or deeper. I don't think there
> is a way to work around that except for not using C2 or deeper
> (not an option) or using a different timer source.
> 
> If that is true then hitting space lots of time will make it 
> go faster.

If that's the case we can even autodetect it and stay with PIT and
ignore lapic all the way.

	tglx


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