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

Kevin Shanahan
2009-01-20T12:42:23Z

On Tue, 2009-01-20 at 12:35 +0100, Ingo Molnar wrote:
> * Kevin Shanahan <kmshanah-biM/RbsGxha6c6uEtOJ/EA@public.gmane.org> wrote:
>
> > On Mon, 2009-01-19 at 22:45 +0100, Rafael J. Wysocki wrote:
> > > This message has been generated automatically as a part of a report
> > > of regressions introduced between 2.6.27 and 2.6.28.
> > >
> > > The following bug entry is on the current list of known regressions
> > > introduced between 2.6.27 and 2.6.28. Please verify if it still should
> > > be listed and let me know (either way).
> > >
> > >
> > > Bug-Entry : http://bugzilla.kernel.org/show_bug.cgi?id=12465
> > > Subject : KVM guests stalling on 2.6.28 (bisected)
> > > Submitter : Kevin Shanahan <kmshanah-biM/RbsGxha6c6uEtOJ/EA@public.gmane.org>
> > > Date : 2009-01-17 03:37 (3 days old)
> >
> > Yes, please keep this on the list.
>
> This only seems to occur under KVM, right? I.e. you tested it with -no-kvm
> and the problem went away, correct?

Well, the I couldn't make the test conditions identical, but it the
problem didn't occur with the test I was able to do:

http://marc.info/?l=linux-kernel&m=123228728416498&w=2

> This suggests some sort of KVM-specific problem. Scheduler latencies in
> the seconds that occur under normal load situations are noticed and
> reported quickly - and there are no such open regressions currently.

It at least suggests a problem with interaction between the scheduler
and kvm, otherwise reverting that scheduler patch wouldn't have made the
regression go away.

Regards,
Kevin.