linux-kernel - Re: [Bug #12465] KVM guests stalling on 2.6.28 (bisected)

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Message-Id: <1237411441.5211.5.camel@kulgan.wumi.org.au>
Date:	Thu, 19 Mar 2009 07:54:01 +1030
From:	Kevin Shanahan <kmshanah@...b.org.au>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Avi Kivity <avi@...hat.com>, "Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>, Mike Galbraith <efault@....de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [Bug #12465] KVM guests stalling on 2.6.28 (bisected)

On Wed, 2009-03-18 at 11:46 +1030, Kevin Shanahan wrote:
> On Wed, 2009-03-18 at 01:20 +0100, Frederic Weisbecker wrote:
> > Ok, I've made a small script based on yours which could do this job.
> > You will just have to set yourself a threshold of latency
> > that you consider as buggy. I don't remember the latency you observed.
> > About 5 secs right?
> > 
> > It's the "thres" variable in the script.
> > 
> > The resulting trace should be a mixup of the function graph traces
> > and scheduler events which look like this:
> > 
> >  gnome-screensav-4691  [000]  6716.774277:   4691:120:S ==> [000]     0:140:R <idle>
> >   xfce4-terminal-4723  [001]  6716.774303:   4723:120:R   + [001]  4289:120:S Xorg
> >   xfce4-terminal-4723  [001]  6716.774417:   4723:120:S ==> [001]  4289:120:R Xorg
> >             Xorg-4289  [001]  6716.774427:   4289:120:S ==> [001]     0:140:R <idle>
> > 
> > + is a wakeup and ==> is a context switch.
> > 
> > The script will loop trying some pings and will only keep the trace that matches
> > the latency threshold you defined.
> > 
> > Tell if the following script work for you.

...

> Either way, I'll try to get some results in my maintenance window
> tonight.

Testing did not go so well. I compiled and booted
2.6.29-rc8-tip-02630-g93c4989, but had some problems with the system
load when I tried to start tracing - it shot up to around 16-20 or so. I
started shutting down VMs to try and get it under control, but before I
got back to tracing again the machine disappeared off the network -
unresponsive to ping.

When I got in this morning, there was nothing on the console, nothing in
the logs to show what went wrong. I will try again, but my next chance
will probably be Saturday. Stay tuned.

Regards,
Kevin.


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