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RE: [Xen-ia64-devel] RE: Xen-ia64-devel Digest, Vol 11, Issue 22

To: "Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>
Subject: RE: [Xen-ia64-devel] RE: Xen-ia64-devel Digest, Vol 11, Issue 22
From: Alex Williamson <alex.williamson@xxxxxx>
Date: Fri, 10 Feb 2006 13:24:17 -0700
Cc: "Luck, Tony" <tony.luck@xxxxxxxxx>, xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
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On Fri, 2006-02-10 at 11:56 -0800, Magenheimer, Dan (HP Labs Fort
Collins) wrote:
> > 
> > What if you are running on h/w where ITC cannot be synchronized
> > because different cpus are driven from different clock sources?
> > See IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT.
> > 
> > Solution d) might be to tell the guest that itc isn't syncronized
> > (even on systems where it could be).
> 
> Cool.  I wasn't aware of this feature.  What are the
> ramifications to an SMP OS (or in this case SMP guest)
> if itc isn't synchronized?  (I see the comment in time.c,
> just not sure I fully understand the user-visible impact.)

   Another time source is required for the time interpolator in that
case.  This is often an HPET or platform specific time source.

        Alex

-- 
Alex Williamson                             HP Linux & Open Source Lab


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