From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933601Ab0J2IaY (ORCPT ); Fri, 29 Oct 2010 04:30:24 -0400 Received: from smtp-out-009.synserver.de ([212.40.180.9]:1126 "EHLO smtp-out-008.synserver.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756013Ab0J2IaU (ORCPT ); Fri, 29 Oct 2010 04:30:20 -0400 X-SynServer-TrustedSrc: 1 X-SynServer-AuthUser: markus@trippelsdorf.de X-SynServer-PPID: 23885 Date: Fri, 29 Oct 2010 10:30:13 +0200 From: Markus Trippelsdorf To: Borislav Petkov , john stultz , Thomas Gleixner , Borislav Petkov , "linux-kernel@vger.kernel.org" , "hpa@linux.intel.com" , Ingo Molnar , Andreas Herrmann , heiko.carstens@de.ibm.com, a.p.zijlstra@chello.nl, avi@redhat.com, mtosatti@redhat.com Subject: Re: [bisected] Clocksource tsc unstable git Message-ID: <20101029083013.GA1553@arch.trippelsdorf.de> References: <20101026112052.GA1672@arch.trippelsdorf.de> <20101026131843.GC17852@aftab> <20101026135808.GB1672@arch.trippelsdorf.de> <1288120736.2645.9.camel@localhost> <20101027142622.GA1555@arch.trippelsdorf.de> <20101027182608.GA1580@arch.trippelsdorf.de> <20101029081831.GA7149@liondog.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20101029081831.GA7149@liondog.tnic> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 29, 2010 at 10:18:31AM +0200, Borislav Petkov wrote: > On Wed, Oct 27, 2010 at 08:26:08PM +0200, markus@trippelsdorf.de wrote: > > During my search for a reliable testcase I found out that kvm guests also > > showed random hangs (that didn't happen in v2.6.36) here. These hangs last a > > few seconds each, during which the mouse is not movable at all. > > > > So I ran git-bisect with this testcase and the result of the bisection is: > > > > 34f971f6f7988be4d014eec3e3526bee6d007ffa is the first bad commit > > commit 34f971f6f7988be4d014eec3e3526bee6d007ffa > > Author: Peter Zijlstra > > Date: Wed Sep 22 13:53:15 2010 +0200 > > > > ... > > > > > Reverting the commit solves the kvm hang issue. (If this issue is > > related to my original tsc problem is of course open for debate, but I > > have a strong hunch it is.) > > Well, what do you know, the temporary "slowdown" triggered on my setup > too. After waiting a minute maybe, the machine recovered and guess what > appeared in dmesg: > > [44729.650859] Clocksource tsc unstable (delta = -8615263009 ns) > [44729.656229] Switching to clocksource hpet > > I've reverted the changeset above and will run without it to check > whether it makes any difference. After further testing I've found out that the tsc- and the kvm-issue are unrelated. IOW I get these "slowdowns" even with 34f971f6f7988be4 reverted. I guess John was right when he wrote: > From your dmesg, I'd guess the hpet is the watchdog clocksource, so I > be on the lookout for hpet related changes. > > Maybe does reverting 995bd3bb5c78f3ff71339803c0b8337ed36d64fb hide the > issue? Because with 995bd3bb5c78f reverted I never had a single "slowdown" here. -- Markus