Re: [Xen-users] Clock drift

[Jefferson Ogata <xen-users@xxxxxxxxxxxx>]

[Re-sending with correct source address.]

On 2008-08-16 01:59, Ray Fadaie wrote:
> I am using Xen on a Quad Core Phenom with 8G of RAM. Everything is fine 
> except the clock! [oh god :((]
> In Dom0 everything works just fine but in DomUs the clock (both system 
> time and the realtime clock (IRQ8) drift. I can live with the system 
> time drift (I just enforce NTP every 5 minutes) but all my applications 
> in DomUs that depend on the realtime clock (IRQ8) are messed up.
> Do you guys have any idea what could be wrong here?
>
> p.s. All DomUs and Dom0 are running CentOS 5 on on a M3A mother board 
> from Assus (64 bit CPU - X4).
I don't understand *why* this happens, but I've seen the same thing, as
have many others (check Google).

I think I've got it under control now. The following works for me:

On dom0:
- Set xen.independent_wallclock = 1 in /etc/sysctl.conf (corresponding
to /proc/sys/xen/independent_wallclock)
- Run ntpd.

On PVM domUs:
- Set xen.independent_wallclock = 1 in /etc/sysctl.conf
- Run ntpd.

On HVM domUs:
- Disable acpi in xen config (acpi = 0).
- Run ntpd.

The clock sometimes still jumps a bit during a live migration, but ntpd
slews it back afterward.

--
Jefferson Ogata : Internetworker, Antibozo

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