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Date: Mon, 21 Jul 2008 22:25:13 +0200 (CEST) From: Thomas Gleixner <tglx@...utronix.de> To: Philippe Troin <phil@...i.org> cc: eric miao <eric.y.miao@...il.com>, Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>, Jack Ren <jack.ren@...vell.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Dmitry Adamushko <dmitry.adamushko@...il.com> Subject: Re: [PATCH] sched: do not stop ticks when cpu is not idle On Mon, 21 Jul 2008, Philippe Troin wrote: > Thomas Gleixner <tglx@...utronix.de> writes: > I've seen weird timer behavior on both i386 and x86_64 on SMP > machines. By weird I mean: > > - time stops for a few hours, then resumes as if nothing happened; > > - time flows too fast or slow (4x faster to 2x slower depending on > phase of the moon); > > - the last one I've seen (yesterday), was: > sleep(1) sleeps for 1 second, but > select(0, NULL, NULL, NULL, 0.5) sleeps for nine seconds. > > I have been trying to track this problem for a few weeks now, without > success. Booting a CONFIG_NO_HZ-enabled kernel with "highres=off > nohz=off" does not make a difference. However booting a kernel with > CONFIG_NO_HZ and CONFIG_HIGH_RES_TIMERS disabled seems to be working > (I cannot garantee that since I've been using that for 48h so far, but > sometimes the problem takes a few days to manifest itself). > > After a cursory reading of your patch, it looks to me that the race > could happen on a kernel compiled with CONFIG_NO_HZ and > CONFIG_HIGH_RES_TIMERS and booted with "nohz=off highres=off". Can > you confirm that? No, I can not confirm that. With nohz=off / highres=off that code path is not invoked. > If you need more details (dmesg, lspci, etc), I have posted some > details on LKML ( http://lkml.org/lkml/2008/7/9/330 ) and I have a bug > posted on the Fedora/RH bugzilla ( > https://bugzilla.redhat.com/show_bug.cgi?id=451824 ). Will have a look. Question: which clocksource is active ? cat /sys/devices/system/clocksource/clocksource0/current_clocksource Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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