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Re: [Xen-devel] comprehensive documentation of clock-related options for

To: Guillaume Rousse <Guillaume.Rousse@xxxxxxxx>
Subject: Re: [Xen-devel] comprehensive documentation of clock-related options for HVM guests
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Tue, 17 Feb 2009 09:41:40 +0000
Cc: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
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On 17/02/2009 08:38, "Guillaume Rousse" <Guillaume.Rousse@xxxxxxxx> wrote:

> Keir Fraser a écrit :
>> It's also worth pointing out that NTP synchronisation in dom0 does not
>> affect HVM guest synchronisation at all. And in general that would be very
>> hard to do in a way that isn't fragile. The only solutions I can see here
>> for absolute time synchronisation are a PV driver or daemon for time
>> handling (which we do not currently have for any type of HVM guest) or
>> perform NTP synchronisation in the guest itself (our time handling should be
>> accurate enough for an ntp daemon to latch onto it).
> That's what (ntp sync in guests) we do, sorry if I wasn't clear. I've
> tried timer_mode=1 yesterday, it seem to have reduced the deviation to
> an acceptable level for every host but one. I'll try to switch to
> timer_mode=2 today.

Good idea. Timer_mode=0 is in general pretty bad. 1 and 2 seem to cover most
guests okay.

 -- Keir



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