From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [Bug #12465] KVM guests stalling on 2.6.28 (bisected) Date: Tue, 20 Jan 2009 12:35:46 +0100 Message-ID: <20090120113546.GA26571@elte.hu> References: <1232410363.4768.21.camel@kulgan.wumi.org.au> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <1232410363.4768.21.camel-9TBizaOOD0ujuAshGpSIhRCuuivNXqWP@public.gmane.org> Sender: kernel-testers-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Kevin Shanahan , Avi Kivity Cc: "Rafael J. Wysocki" , Linux Kernel Mailing List , Kernel Testers List , Kevin Shanahan , Mike Galbraith , Peter Zijlstra * Kevin Shanahan wrote: > On Mon, 2009-01-19 at 22:45 +0100, Rafael J. Wysocki wrote: > > This message has been generated automatically as a part of a report > > of regressions introduced between 2.6.27 and 2.6.28. > > > > The following bug entry is on the current list of known regressions > > introduced between 2.6.27 and 2.6.28. Please verify if it still should > > be listed and let me know (either way). > > > > > > Bug-Entry : http://bugzilla.kernel.org/show_bug.cgi?id=12465 > > Subject : KVM guests stalling on 2.6.28 (bisected) > > Submitter : Kevin Shanahan > > Date : 2009-01-17 03:37 (3 days old) > > Yes, please keep this on the list. This only seems to occur under KVM, right? I.e. you tested it with -no-kvm and the problem went away, correct? This suggests some sort of KVM-specific problem. Scheduler latencies in the seconds that occur under normal load situations are noticed and reported quickly - and there are no such open regressions currently. Avi, can you reproduce these latencies? A possibly theory would be some sort of guest wakeup problem/race triggered by a shift in preemption/scheduling patterns. Or something related to preempt-notifiers (which KVM is using). A genuine scheduler bug is in the cards too, but the KVM-only angle of this bug gives it a low probability. Ingo