linux-kernel - Re: nohz and strange sleep latencies

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Message-ID: <20071126115417.GB4701@ucw.cz>
Date:	Mon, 26 Nov 2007 11:54:18 +0000
From:	Pavel Machek <pavel@....cz>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Ingo Molnar <mingo@...e.hu>,
	kernel list <linux-kernel@...r.kernel.org>
Subject: Re: nohz and strange sleep latencies

Hi!

> > > but perhaps somehow we miss this fact and fail to turn off the lapic 
> > > clockevents drivers?
> > 
> > Ok, I guess I'm lost. If I offline second CPU, I immediately get
> > 1000Hz timer tick... is that expected?
> 
> Hmm. No. I have no idea why this is happening.
> 
> 34196 total events, 55.083 events/sec
> echo 0 >/sys/devices/system/cpu/cpu1/online
> 36073 total events, 54.679 events/sec

It happened again, this time on 2.6.24-pre-rc1 (mostly untainted).
Reboot and problem goes away... so this one is random :-(.

I'll try plug/unplug loops, perhaps that can trigger it reliably. (cpu
replug does not fix it once triggered).
							Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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