Re: PCI pass-through of NIC to PV DomU... worth it?

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Fri, Feb 24, 2012 at 07:21:01AM -0500, David Howland wrote:
> On 2/24/2012 6:11 AM, Manuel Bouyer wrote:
> >On Thu, Feb 23, 2012 at 10:51:07PM -0500, David Howland wrote:
> >>I need to know which is faster: the PV network interface or passing
> >>the NIC?  I don't have VT-d support, but the server is a dual
> >>quad-core Xeon setup, so I shouldn't be short on compute cycles.  My
> >>gut is telling me that there wouldn't be any tangible difference,
> >>but I want to hear what the experts think.
> >
> >Running the NIC driver in the domU may help with latency, as it'll
> >avoid context switches between dom0 and domU. Also, you'll be able
> >to use checksum offloads.
> >
> 
> My assumption was that PCI pass-through to a PV host would still use
> reflected memory to move data to dom0 like xennet would.  Is that
> incorrect?

It is. The driver runs in the guest's kernel, and talks directly with the
device.

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