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

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

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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