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

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Date:	Thu, 5 Oct 2006 10:17:25 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Andrew Morton <akpm@...l.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	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>
Subject: Re: [patch 00/22] high resolution timers / dynamic ticks - V3

* Andrew Morton <akpm@...l.org> wrote:

> With CONFIG_HIGH_RES_TIMERS=y, CONFIG_NO_HZ=n it's pretty sick.  It 
> pauses for several seconds after "input: AlpsPS/2 ALPS GlidePoint as 
> /class/input/input2" (printk-time claims 2 seconds, but it was longer 
> than that).
> 
> It's been stuck for a minute or more at the 12.980000 time, seems to 
> have hung.  The cursor is flashing extremely slowly.

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)

We'll figure out a way to detect this hardware sickness (which is 
unrelated to our patchset), for now your workaround is either to turn 
off local-apic-timer support (either in the config or on the kernel 
bootline, in which case the high-res code will fall back to the PIT), or 
to turn off high-res timers (either in the config or on the kernel 
bootline).

	Ingo
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