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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 23:07:17 +0000
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Tue, 20 Nov 2007 15:02:20 -0800
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: Acgryhg7Vp3mGpe9EdyZBAAWy6hiGQ==
  • Thread-topic: [Xen-devel] Xen 3.1.2 domU clock goes out of sync

On 20/11/07 21:52, "Tõnu Raitviir" <jussuf@xxxxxxxx> wrote:

>> 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.
> Well... in the example in my first letter dom0 was booted without ntpd and
> after 2+ days its clock offset was only -0.438055 while domU had drifted
> far away. In that case there was no adjustment values to remember.

Could it not be a drift? e.g., Perhaps you ran ntpdate in dom0 but not the

>> So... running ntpd in dom0 is a good idea. :-)
> I don't question that. But I wonder, isn't domU clock supposed to be
> always in sync with dom0, with or without ntpd? Or how exactly does ntpd
> in dom0 affect domU clock?

dom0 updates Xen's shared notion of wallclock time periodically, but only if
dom0 is locked onto ntp.

 -- Keir

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