[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <alpine.DEB.1.10.0901212044450.1737@gandalf.stny.rr.com>
Date: Wed, 21 Jan 2009 20:48:00 -0500 (EST)
From: Steven Rostedt <rostedt@...dmis.org>
To: Avi Kivity <avi@...hat.com>
cc: Kevin Shanahan <kmshanah@...b.org.au>, Ingo Molnar <mingo@...e.hu>,
"Rafael J. Wysocki" <rjw@...k.pl>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Kernel Testers List <kernel-testers@...r.kernel.org>,
Mike Galbraith <efault@....de>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Frédéric Weisbecker <fweisbec@...il.com>,
bugme-daemon@...zilla.kernel.org
Subject: Re: [Bug #12465] KVM guests stalling on 2.6.28 (bisected)
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 fixed up the wakeup latency tracer to work with all tasks (as well as
other fixes). You can checkout the following:
git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git
branch: tip/devel
compile with CONFIG_FUNCTION_TRACER and CONFIG_SCHED_TRACER and just
echo 0 > /debug/tracing/tracing_enabled
echo wakeup > /debug/tracing/current_tracer
echo 1 > /debug/tracing/tracing_enabled
run your test
echo 0 > /debug/tracing/tracing_enabled
and then look at /debug/tracing/latency_trace
-- Steve
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists