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Re: [Xen-devel] time jumping back and forth

To: David Becker <becker@xxxxxxxxxxx>
Subject: Re: [Xen-devel] time jumping back and forth
From: Ian Pratt <Ian.Pratt@xxxxxxxxxxxx>
Date: Mon, 27 Sep 2004 17:28:46 +0100
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxxx, Ian.Pratt@xxxxxxxxxxxx
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> 
> I am have been seeing xen0 time jump around all weekend.   I have not been
> able to pin down a way to reproduce the problem.   
> 
> It will appear like the clocks are drifting unlocked from ntp and then
> suddenly most are right on time.  A while later some clocks are off an
> hour and some are fine.   Sometimes checking or setting hwclock makes
> thing jump.  Some hosts seem more prone to it than others.

Are you 100% sure it worked before? The only time related change
is 1.1338.1.1 "Leave the TSC cpu feature bit set. ", but I'd be
very surprised if this changed the behaviour of NTP.

> This is with the today's pull, changeset 1.1347 and running ntpd 4.2.0a
> I'm wondering if ntpd is having trouble synchronizing to its server.

ntpq then 'peers' should tell you this. I wouldn't expect to seem
time jumping by an hour, though. 

Hmm, I wander if its something daft to do with hwclock being UTC
or local time?

Are you running anything which is trying to set the hwclock in
dom0? It's best to leave well alone and let Xen do this.

Ian




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