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[Xen-devel] RE: [PATCH] trust new architecturally-defined TSC Invariant

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>, "Xen-Devel (E-mail)" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] RE: [PATCH] trust new architecturally-defined TSC Invariant bit on Intel systems
From: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Date: Fri, 9 Oct 2009 12:03:15 -0700 (PDT)
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> > If TSC is reliable, is it still necessary to rendezvous?
> > I thought the rendezvous was only needed if the slopes
> > differ (but not sure I've thought it all the way through).
> > No sense stealing all those pcpu cycles to rendezvous if
> > it's not necessary, especially on a large system.
> > (Maybe TSC reliability IS useful for Xen, not just for
> > exposing to userland :-)
> 
> Possibly not, but I was only reworking your original patch 
> which didn't
> avoid rendezvous either.

Actually it did (avoid rendezvous), but I have to admit
it was accidental: I was trying to avoid the write_tsc's
not the rendezvous, and I didn't notice the additional
implication until I was looking at the difference between
my patch and yours.

I'll look at this more in a few days...

Dan

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