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Re: [Xen-devel] Xen 3.1.2 domU clock goes out of sync

  • To: Tõnu Raitviir <jussuf@xxxxxxxx>
  • From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
  • Date: Tue, 20 Nov 2007 19:30:30 +0000
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Tue, 20 Nov 2007 11:25:04 -0800
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: Acgrq890DbqTKJefEdyZBAAWy6hiGQ==
  • Thread-topic: [Xen-devel] Xen 3.1.2 domU clock goes out of sync

I wonder if dom0 has remembered some ntp-derived adjustment values despite
ntpd no longer running. That would explain why it continues to keep good
time while all others drift. The others drifting is quite explicable -- they
are only as accurate as our estimate of platform timer (PIT or HPET)
frequency at boot time, and the accuracy of the crystal that drives that
timer is probably only good to about 100ppm.

So... running ntpd in dom0 is a good idea. :-)

 -- Keir

On 20/11/07 19:15, "Tõnu Raitviir" <jussuf@xxxxxxxx> wrote:

> On Tue, 20 Nov 2007, Keir Fraser wrote:
>> Do all domUs stay in sync with each other, or do all guests drift randomly?
> I didn't compare domU-s before, but they seem to be in sync. I stopped
> ntpd on dom0 five hours ago, and now the results of ntpdate are:
> dom0    offset -0.002353 sec
> domU #1 offset -1.555219 sec
> domU #2 offset -1.555261 sec
> domU #3 offset -1.555243 sec

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