Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755922AbYGUUZz (ORCPT ); Mon, 21 Jul 2008 16:25:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753140AbYGUUZq (ORCPT ); Mon, 21 Jul 2008 16:25:46 -0400 Received: from www.tglx.de ([62.245.132.106]:35905 "EHLO www.tglx.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751373AbYGUUZp (ORCPT ); Mon, 21 Jul 2008 16:25:45 -0400 Date: Mon, 21 Jul 2008 22:25:13 +0200 (CEST) From: Thomas Gleixner To: Philippe Troin cc: eric miao , Ingo Molnar , LKML , Jack Ren , Peter Zijlstra , Dmitry Adamushko Subject: Re: [PATCH] sched: do not stop ticks when cpu is not idle In-Reply-To: <87abgb3vay.fsf@old-tantale.fifi.org> Message-ID: References: <20080718102446.GV6875@elte.hu> <87abgb3vay.fsf@old-tantale.fifi.org> User-Agent: Alpine 1.10 (LFD 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1870 Lines: 49 On Mon, 21 Jul 2008, Philippe Troin wrote: > Thomas Gleixner 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@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/