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Re: [Xen-devel] [PATCH RFC] xenbus_client: extend interface to suppurt multi-page ring

On Thu, May 30, 2013 at 03:09:12PM +0100, Wei Liu wrote:
> On Thu, May 30, 2013 at 03:06:00PM +0100, Wei Liu wrote:
> > Originally Xen PV drivers only use single-page ring to pass along
> > information. This might limit the throughput between frontend and
> > backend as they can easily run out of ring slots if hardware is fast.
> > 
> > The patch extends Xenbus driver to support multi-page ring, which in
> > general should improve throughput. Changes to various frontend / backend
> > to adapt to the new interface are also included.
> > 
> > Affected Xen drivers:
> > * blkfront/back
> > * netfront/back
> > * pcifront/back
> > 
> > The interface is documented, as before, in xenbus_client.c.
> > 
> Please note that this patch won't apply cleanly on upstream kernel as it
> relies on some patches that are not in tree.

> I mainly want to collect views on the interface.  Also in the HVM case I
> use vmap, I would like to know if I get it right.

This patches looks familiar that I had seen some time ago (maybe I even
backported it for PV?). Anyhow the PV part looks OK.

The HVM - I don't see why we cannot do vmap. The nature of the ring is that
it stays mapped for a very long time - so using vmap is OK. That is, the
issues with vmap is that it takes a bit to setup and teardown - and that
is OK with us.

If you would like to rebase it on top of v3.11-rc5 and repost it I don't
see why we can't have it for v3.12. David, Boris?

> Thanks
> Wei.
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