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

Kevin Shanahan
2009-03-18T21:24:01Z

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.