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

David Boutcher
2006-05-09T14:31:01Z

virtualization-bounces@lists.osdl.org wrote on 05/09/2006 09:00:27 AM:
> 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.

Then make a generic solution. VMWare supports migration, the Power
virtualization will get around to it eventually. All will need something
similar. So either make a common user-land tool, or (if you insist on
incorrectly driving this into the kernel) add some kind of common hook to
the TCP/IP stack.

Dave Boutcher
IBM Linux Technology Center