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

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>, "Xen-Devel (E-mail)" <xen-devel@xxxxxxxxxxxxxxxxxxx>, "Tian, Kevin" <kevin.tian@xxxxxxxxx>
Subject: RE: [Xen-devel] Time goes backwards in dom0 in xen-unstable
From: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Date: Wed, 15 Apr 2009 14:22:01 +0000 (GMT)
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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
> 
> 
> 
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> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel
>

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