On Sun, Sep 11, 2005 at 07:16:27PM +0100, David Laight wrote:
> On Sun, Sep 11, 2005 at 06:42:07PM +0200, Manuel Bouyer wrote:
> > Hi,
> > this is a question for UVM gurus :)
> > I'm trying to implement 0-copy in xen's network backend, and have to solve
> > a VM issue.
> 
> It is actually worth doing some checks that the 0-copy is actually
> a performace gain.
> You might find that a fast data copy [1] is quicker than all the TLB and VM
> manipulations that are needed for the page loaning.

Sure. But in this case, we have to map the page in domain0 to be able
to copy it anyway. Maybe there's a way to do a copy using physical addresses
only, but remember that under Xen the NetBSD kernel runs in ring 1, not
ring 0 ...

-- 
Manuel Bouyer <bouyer@antioche.eu.org>
     NetBSD: 26 ans d'experience feront toujours la difference
--