Re: [PATCH 1/5] Add a global synchronization point for pvclock

[Zachary Amsden]

On 04/20/2010 09:42 AM, Jeremy Fitzhardinge wrote:
> On 04/20/2010 11:54 AM, Avi Kivity wrote:
>    
> > On 04/20/2010 09:23 PM, Jeremy Fitzhardinge wrote:
> >      
> > > On 04/20/2010 02:31 AM, Avi Kivity wrote:
> > >
> > >        
> > > > btw, do you want this code in pvclock.c, or shall we keep it kvmclock
> > > > specific?
> > > >
> > > >          
> > > I think its a pvclock-level fix.  I'd been hoping to avoid having
> > > something like this, but I think its ultimately necessary.
> > >
> > >        
> > Did you observe drift on Xen, or is this "ultimately" pointing at the
> > future?
> >      
> People are reporting weirdnesses that "clocksource=jiffies" apparently
> resolves.  Xen and KVM are faced with the same hardware constraints, and
> it wouldn't surprise me if there were small measurable
> non-monotonicities in the PV clock under Xen.  May as well be safe.
>    

Does the drift only occur on SMP VMs?

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