Re: [Qemu-devel] high outage times for qemu virtio network links during live migration, trying to debug

[Chris Friesen]

On 01/26/2016 10:45 AM, Daniel P. Berrange wrote:
> On Tue, Jan 26, 2016 at 10:41:12AM -0600, Chris Friesen wrote:

> > My question is, why doesn't qemu continue processing virtio packets while
> > the dirty page scanning and memory transfer over the network is proceeding?
>
> The qemuDomainMigratePrepareTunnel3Params() method is responsible for
> starting the QEMU process on the target host. This should not normally
> have any impact on host networking connectivity, since the CPUs on that
> target QEMU wouldn't be running at that point. Perhaps the mere act of
> starting QEMU and plugging the TAP dev into the network on the target
> host causes some issue though ? eg are you using a bridge that is doing
> STP or something like that.

Well, looks like your suspicions were correct.  Our fast-path backend was 
mistakenly sending out a GARP when the backend was initialized as part of 
creating the qemu process on the target host.  Oops.

Thanks for your help.

Chris