On 26/01/2016 17:41, Chris Friesen wrote: > I'm using libvirt (1.2.12) with qemu (2.2.0) in the context of OpenStack. > > If I live-migrate a guest with virtio network interfaces, I see a > ~1200msec delay in processing the network packets, and several hundred > of them get dropped. I get the dropped packets, but I'm not sure why > the delay is there. > > I instrumented qemu and libvirt, and the strange thing is that this > delay seems to happen before qemu actually starts doing any > migration-related work. (i.e. before qmp_migrate() is called) > > Looking at my timestamps, the start of the glitch seems to coincide with > libvirtd calling qemuDomainMigratePrepareTunnel3Params(), and the end of > the glitch occurs when the migration is complete and we're up and > running on the destination. > > My question is, why doesn't qemu continue processing virtio packets > while the dirty page scanning and memory transfer over the network is > proceeding? QEMU (or vhost) _are_ processing virtio traffic, because otherwise you'd have no delay---only dropped packets. Or am I missing something? Paolo -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list