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xen-devel
Re: [Xen-devel] Re: Next steps with pv_ops for Xen
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xen-devel@xxxxxxxxxxxxxxxxxxx |
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Subject: |
Re: [Xen-devel] Re: Next steps with pv_ops for Xen |
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From: |
Mark Williamson <mark.williamson@xxxxxxxxxxxx> |
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Date: |
Mon, 3 Dec 2007 17:18:23 +0000 |
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Cc: |
Derek Murray <Derek.Murray@xxxxxxxxxxxx>, Eduardo Habkost <ehabkost@xxxxxxxxxx>, Juan Quintela <quintela@xxxxxxxxxx>, "Stephen C. Tweedie" <sct@xxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxxxx>, Glauber de Oliveira Costa <gcosta@xxxxxxxxxx>, Chris Wright <chrisw@xxxxxxxxxxxx>, "virtualization@xxxxxxxxxxxxxx" <virtualization@xxxxxxxxxxxxxx>, Gerd Hoffmann <kraxel@xxxxxxxxxx> |
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Mon, 03 Dec 2007 09:19:31 -0800 |
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> >> It gets better, though. The same hook is used in the version of blktap
> >> in linux-2.6.18-xen (not, as far as I can see, in the sparse tree for
> >> xen-3.1-testing):
> >
> > Oh, I'm thinking more in the direction of killing blktap altogether in
> > favor of a pure userspace implementation on top of gntdev.
>
> I think this would represent good progress, though I wonder if there
> would be a performance penalty due to performing the mapping and
> unmapping in user-space (multiple syscalls per mapping versus a single
> hypercall).
Maybe a change to the gntdev userspace API to allow batching of mapping
requests?
I'm not aware of a batched mmap interface, which would seem to be the ideal
solution; but it should be possible to batch this stuff somehow. Although it
seems like some kind of really weird ioctl might be needed :-S to do it
*without* such a batched interface...
blktap in userspace, if any performance problems can be addressed, would seem
to be a far nicer way of doing things. And it's less code to merge
upstream ;-)
Cheers,
Mark
--
Dave: Just a question. What use is a unicyle with no seat? And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!
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