RE: [Xen-devel] Time goes backwards in dom0 in xen-unstable

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

Double hmmm... after destroying the domain and restarting
it has been running fine for over two hours.  So
apparently it was a coincidence.

> -----Original Message-----
> From: Dan Magenheimer 
> Sent: Wednesday, April 15, 2009 8:59 AM
> To: Dan Magenheimer; Keir Fraser; Xen-Devel (E-mail); Tian, Kevin
> Subject: RE: [Xen-devel] Time goes backwards in dom0 in xen-unstable
> 
> 
> Hmmm... after only a few minutes with cpuidle=off,
> my test domPV froze up after printing a number of
> call traces starting with:
> 
> INFO: task xxx:nnn blocked for more than 480 seconds.
> 
> At the top of all of the traces is either
> getnstimeofday+51 or io_schedule+44.
> 
> (Note that this PV domain is a 2.6.29 kernel... don't
> know if the messages are the same on an older kernel.)
> 
> > -----Original Message-----
> > From: Dan Magenheimer 
> > Sent: Wednesday, April 15, 2009 8:22 AM
> > To: Keir Fraser; Xen-Devel (E-mail); Tian, Kevin
> > Subject: RE: [Xen-devel] Time goes backwards in dom0 in xen-unstable
> > 
> > 
> > I can confirm that cpuidle=off makes the timer_interrupt
> > scaleability problem go away.
> > 
> > It also appears that the max cycles for the MSI
> > interrupts becomes reasonably small again.  Was
> > this expected?
> > 
> > I'll leave it running for awhile but may not be
> > able to confirm the "Time went backwards" error
> > goes away as it seemed to appear only after a
> > random long period of time.
> > 
> > (BTW, Kevin, hpetbroadcast did not make the problem
> > go away.)
> > 
> > Dan
> > 
> > > -----Original Message-----
> > > From: Keir Fraser [mailto:keir.fraser@xxxxxxxxxxxxx]
> > > Sent: Wednesday, April 15, 2009 1:31 AM
> > > To: Dan Magenheimer; Xen-Devel (E-mail)
> > > Subject: Re: [Xen-devel] Time goes backwards in dom0 in 
> xen-unstable
> > > 
> > > 
> > > On 14/04/2009 20:36, "Dan Magenheimer" 
> > > <dan.magenheimer@xxxxxxxxxx> wrote:
> > > 
> > > > I'm seeing some "Time went backwards" errors reported
> > > > in dom0 in near-tip (c/s 19515) xen-unstable build.
> > > > It's rare and random and not reproducible, but here's
> > > > the report that just showed up.  There was no load
> > > > running at the time.
> > > > 
> > > > I can move to 3.4-rc1 if that would be helpful but I
> > > > don't remember seeing any time-related changes recently.
> > > > 
> > > > This was on my dual-core test machine which reports
> > > > lots of power management info during Xen boot.
> > > 
> > > If you specify 'cpuidle=off' as a Xen boot parameter, does 
> > > that make the
> > > timer_interrupt scalability problem go away, and this 
> time backwards
> > > problem? I was going to enable by default in 3.4 but could go 
> > > the other way.
> > > 
> > >  -- Keir
> > > 
> > > 
> > > 
> > > _______________________________________________
> > > Xen-devel mailing list
> > > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > > http://lists.xensource.com/xen-devel
> > >

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