Re: [Xen-users] Clock drift

[Antibozo <xen-users@xxxxxxxxxxxx>]

On 2008-08-25 17:04, Eric Ross wrote:
> Did you look into setting your clocksource to jiffies, that seemed to
> help with my live migration issues.
Explicitly setting clocksource to jiffies made things worse if anything. 
IIRC it was the default anyway in most cases.
> I struggled with time drift for months, I was running the same
> configuration you were (except I didn't have any HVMs).  Then I tried
> the following:
>
> Dom0:
>  independent wallclock = 1
>  ntpd
>  clocksource = jiffies
>
> DomU:
>  independent wallclock = 0
>  clocksource = jiffies
>
> I've been monitoring my Dom0s and DomUs with Hyperic for a few months
> (specifically looking at ntp drift) and these settings produce the
> closest numbers to a "bare metal" machine in my environment.
As I say, my problem is under control. independent_wallclock anywhere 
possible, acpi off on HVMs, ntpd everywhere. Only bummer is HVMs don't 
shut down all the way without acpi.
Top posting sucks.

> Jefferson Ogata wrote:
> > 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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