Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760881AbZATLgb (ORCPT ); Tue, 20 Jan 2009 06:36:31 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758330AbZATLgU (ORCPT ); Tue, 20 Jan 2009 06:36:20 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:46245 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751243AbZATLgT (ORCPT ); Tue, 20 Jan 2009 06:36:19 -0500 Date: Tue, 20 Jan 2009 12:35:46 +0100 From: Ingo Molnar To: Kevin Shanahan , Avi Kivity Cc: "Rafael J. Wysocki" , Linux Kernel Mailing List , Kernel Testers List , Kevin Shanahan , Mike Galbraith , Peter Zijlstra Subject: Re: [Bug #12465] KVM guests stalling on 2.6.28 (bisected) Message-ID: <20090120113546.GA26571@elte.hu> References: <1232410363.4768.21.camel@kulgan.wumi.org.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1232410363.4768.21.camel@kulgan.wumi.org.au> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1620 Lines: 38 * 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 -- 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/