Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759828AbZATMif (ORCPT ); Tue, 20 Jan 2009 07:38:35 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754370AbZATMiZ (ORCPT ); Tue, 20 Jan 2009 07:38:25 -0500 Received: from mx2.redhat.com ([66.187.237.31]:42313 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752190AbZATMiY (ORCPT ); Tue, 20 Jan 2009 07:38:24 -0500 Message-ID: <4975C586.8090605@redhat.com> Date: Tue, 20 Jan 2009 14:37:26 +0200 From: Avi Kivity User-Agent: Thunderbird 2.0.0.19 (X11/20090105) MIME-Version: 1.0 To: Ingo Molnar CC: Kevin Shanahan , "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) References: <1232410363.4768.21.camel@kulgan.wumi.org.au> <20090120113546.GA26571@elte.hu> In-Reply-To: <20090120113546.GA26571@elte.hu> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1962 Lines: 56 Ingo Molnar wrote: > * 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. > > Not necessarily. -no-kvm runs with only one thread, compared to kvm that runs with 1 + nr_cpus threads. > Avi, can you reproduce these latencies? No. > 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. > Can we trace task wakeups somehow? (latency between wakeup and actually running). -- error compiling committee.c: too many arguments to function -- 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/