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RE: [Xen-devel] clock drift in Xen 4.0.0

To: "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx>, "Jeremy Fitzhardinge" <jeremy@xxxxxxxx>
Subject: RE: [Xen-devel] clock drift in Xen 4.0.0
From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Date: Wed, 26 May 2010 23:26:23 +1000
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Thread-topic: [Xen-devel] clock drift in Xen 4.0.0
> >> What domU and dom0 kernel are you running?  pvops always has
> > independent
> >> wallclock.
> >
> > Dom0 is (pvops), domU is (not pvops). Which one
> > matters here?
> I think pv_ops doesn't play with dependent-wallclock either way round:
> won't resync its wallclock with Xen when running as domU; nor will it
> periodically push its wallclock down to Xen when running as dom0. So
if you
> have pv_ops as the dom0 or the domU, you'd better run NTP in the domU.

Just for the record, with a pvops dom0 and a non-pvops domu, you still
need to set independent_wallclock=1 for ntp to be able to modify the
clock. Without that change, ntp tells me:

time reset -409.699016 s
time reset -409.776693 s
time reset -409.854404 s
time reset -409.930385 s
time reset -410.009187 s

but never actually adjusts the time!


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