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

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Message-ID: <20090325234806.GO5932@nowhere>
Date:	Thu, 26 Mar 2009 00:48:07 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Kevin Shanahan <kmshanah@...b.org.au>
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 Thu, Mar 26, 2009 at 10:10:32AM +1030, Kevin Shanahan wrote:
> On Tue, 2009-03-24 at 12:44 +0100, Frederic Weisbecker wrote:
> > Sorry, I've been late to answer.
> > As I explained in my previous mail, you trace is only
> > a snapshot that happened in 10 msec.
> > 
> > I experimented different sizes for the ring buffer but even
> > a 1 second trace require 20 Mo of memory. And a so huge trace
> > would be impractical.
> > 
> > I think we should keep the trace filters we had previously.
> > If you don't minde, could you please retest against latest -tip
> > the following updated patch? Iadded the filters, fixed the python
> > subshell and also flushed the buffer more nicely according to
> > a recent feature in -tip:
> > 
> > echo > trace 
> > 
> > instead of switching to nop.
> > You will need to pull latest -tip again.
> 
> Ok, thanks for that. I'll get a new -tip kernel ready to test tonight.
> I'm not sure about the change to the python subshell though:
> 
> > while [ "$found" != "True" ]
> > do
> >         # Flush the previous buffer
> >         echo trace > $prefix/trace
> > 
> >         echo 1 > $prefix/tracing_enabled
> >         lat=$(ping -c 1 $addr | grep rtt | grep -Eo " [0-9]+.[0-9]+")
> >         echo 0 > $prefix/tracing_enabled
> > 
> > 	echo $lat
> > 	found=$(python -c "print float(str($lat).strip())")
> >         sleep 0.01
> > done
> 
> kmshanah@...gan:~$ python -c "print float(str(1.234).strip())"
> 1.234
> 
> That's not going to evaluate to "True" at all is it? What happened to
> the test against the latency threshold value? Did you mean something
> like this?
> 
> kmshanah@...gan:~$ python -c "print float(str(1.234).strip()) > 5000"
> False
> kmshanah@...gan:~$ python -c "print float(str(5001.234).strip()) > 5000"
> True


Sorry. I guess I was a bit asleep.
It's a mistake. So you can restore how it was.

Thanks.

 
> Cheers,
> Kevin.
> 
> 

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