Re: [libvirt] 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.
Unfortunately, to libvirt 'port data' are opaque blob. And I'm not sure
we can know in advance what ports have data to transfer and which don't.
Michal