Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758790AbZAUPOT (ORCPT ); Wed, 21 Jan 2009 10:14:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753480AbZAUPOD (ORCPT ); Wed, 21 Jan 2009 10:14:03 -0500 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.123]:62939 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752527AbZAUPOB (ORCPT ); Wed, 21 Jan 2009 10:14:01 -0500 Date: Wed, 21 Jan 2009 10:13:59 -0500 (EST) From: Steven Rostedt X-X-Sender: rostedt@gandalf.stny.rr.com To: Avi Kivity cc: Kevin Shanahan , Ingo Molnar , "Rafael J. Wysocki" , Linux Kernel Mailing List , Kernel Testers List , Mike Galbraith , Peter Zijlstra , =?ISO-8859-15?Q?Fr=E9d=E9ric_Weisbecker?= , bugme-daemon@bugzilla.kernel.org Subject: Re: [Bug #12465] KVM guests stalling on 2.6.28 (bisected) In-Reply-To: <49773848.4080409@redhat.com> Message-ID: References: <1232410363.4768.21.camel@kulgan.wumi.org.au> <20090120113546.GA26571@elte.hu> <1232455343.4895.4.camel@kulgan.wumi.org.au> <20090120125652.GA1457@elte.hu> <20090120130714.GA11048@elte.hu> <49760E2D.2060109@redhat.com> <1232547932.4895.119.camel@kulgan.wumi.org.au> <49773275.3020203@redhat.com> <1232549502.4895.124.camel@kulgan.wumi.org.au> <49773848.4080409@redhat.com> User-Agent: Alpine 1.10 (DEB 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: 1829 Lines: 50 On Wed, 21 Jan 2009, Avi Kivity wrote: > Kevin Shanahan wrote: > > > > --- hermes-old.wumi.org.au ping statistics --- > > > > 900 packets transmitted, 900 received, 0% packet loss, time 899326ms > > > > rtt min/avg/max/mdev = 0.093/0.157/3.611/0.117 ms > > > > > > > > So, a _huge_ difference. But what does it mean? > > > > > > > It means, a scheduling problem. Can you run the latency tracer (which > > > only works with realtime priority), so we can tell if it is (a) kvm > > > failing to wake up the vcpu properly or (b) the scheduler delaying the > > > vcpu from running. > > > > > > > Sorry, but are you sure that's going to be useful? > > > > If it only works on realtime threads and I'm not seeing the problem when > > running kvm with realtime priority, is this going to tell you what you > > want to know? > > > > Not trying to be difficult, but that just didn't make sense to me. > > > > You're right, wasn't thinking properly. > > This is a tough one. I'll see if I can think of something. Ingo, any ideas? > I should have replied to this email :-) Yeah, I'm working on making wakeup latency tracer work with non rt tasks. The "wakeup" tracer will now trace all tasks where as a new "wakeup_rt" tracer will only trace rt tasks. I did it for rt tasks only because it only records the highest latency wake ups and the non rt tasks were always bigger than the rt tasks which made what I was tracing useless (the rt scheduling). But by not having an option for all tasks, it makes the wakeup tracer useless for everyone else ;-) -- Steve -- 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/