Re: [libvirt] Question about save and restore OVS per-port data in live migration

> -----Original Message----- > From: Michal Privoznik [mailto:mprivozn@redhat.com] > Sent: Wednesday, May 29, 2019 3:44 PM > To: wangxin (U) <wangxinxin.wang(a)huawei.com>; libvir-list(a)redhat.com > Cc: Lichunhe (Cloud Networking) <lichunhe(a)huawei.com&gt; > Subject: Re: Question about save and restore OVS per-port data in live > migration > > On 5/29/19 6:23 AM, wangxin (U) wrote: >> Hi >> >> When we try to migrate a guest with 12 NICs, we find libvirt will try >> to get per-port data in finish phase, it makes the guest paused for >> several hundred milliseconds. >> >> qemuMigrationCookieAddNetwork >> -> virNetDevOpenvswitchGetMigrateData for per-nic >> -> run 'ovs-vsctl --if-exists get Interface vnetx external_ids:Port' > (about 25ms) >> >> In our case, there's no portData available and it seems there is no need to > run the cmd. >> >> Questions: >> 1. Is it necessary to get/set per-port data in migration finish phase? It will > increase the downtime. >> 2. Is there any way (i.e. a switch) to not run the OVS cmd if there's no > portData available? >> > > IIUC migrating port data is required for openvswitch functionality on > the destination. Although looking at the commit that introduced this > does not say that explicitly (v1.0.0-rc1~8). But I vaguely recall that > being the case. We should revisit that decission and ask ovd guys if > that's still the case. It will be helpful to do this. And, is there a special reason to migrating port data in finish phase? The finish phase should be as simple as possible.