Re: [Xen-devel] [RFC PATCH 34/35] Add the Xen virtual network device driver.

Christian Limpach
2006-05-09T14:00:42Z

On Tue, May 09, 2006 at 11:26:03PM +1000, Herbert Xu wrote:
> Christian Limpach <Christian.Limpach@cl.cam.ac.uk> wrote:
> >
> > Possibly having to page in the process and switching to it would add
> > to the live migration time. More importantly, having to install an
> > additional program in the guest is certainly not very convenient.
>
> Sorry I'm still not convinced. What's there to stop me from suspending
> my laptop to disk, moving it from port A to port B and resuming it?
>
> Wouldn't I be in exactly the same situation? By the same reasoning we'd
> be adding a gratuitous ARP routine to every single laptop network driver.

It is the same situation except that in the laptop case you don't care
that reconfiguring your network will take a second or a few. For live
migration we're looking at network downtime from as low as 60ms to
something like 210ms on a busy virtual machine. I'm not saying that
a userspace solution wouldn't work but it would probably add a measurable
delay to the network downtime during live migration.

You might also find the following paper an interesting read:
http://www.cl.cam.ac.uk/Research/SRG/netos/papers/2005-migration-nsdi-pre.pdf

christian