WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-ia64-devel

Re: [Xen-ia64-devel] SMP-guest status

On Thu, 2006-04-20 at 15:22 +0200, Tristan Gingold wrote:
> Le Jeudi 20 Avril 2006 05:47, Alex Williamson a écrit :
> >    Is the jitter protection in the time interpolator sufficient for
> > ignoring this?  Drift is really meant to indicate the ITCs are driven
> > from different time sources so may run at slightly different clock
> > frequencies.  Seems we should only need to provide that flag to the
> > guest if the platform firmware set it.  As long as the ITCs are nearly
> > synchronized, the jitter protection in the ITC interpolator will prevent
> > time from going backwards.  This would then get rid of the change in
> > time.c.  Thanks,
> The change in time.c is just to work around a kernel bug.  Linux kernel 
> requires at least an interpolator. [Hence I think there is no platform 
> without ITC drift].

   I'm not sure I'd call it a bug.  The kernel requires some kind of
timesource for an interpolator.  AFAIK, SGI systems are the only ones
that report ITC drift and they have a platform timesource to compensate.
HPET support is another, more generic, way to do this.  If this is a
temporary workaround, I think it would be more clear to use
running_on_xen as a flag to indicate ITCs are pre-synchronized and not
report platform ITC drift via the features table.  Thanks,

        Alex

-- 
Alex Williamson                             HP Linux & Open Source Lab


_______________________________________________
Xen-ia64-devel mailing list
Xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-ia64-devel