On Tue, Jan 05, 2021 at 21:54:05 +0800, Keqian Zhu wrote:
On 2021/1/5 21:34, Daniel P. Berrangé wrote:
On Tue, Jan 05, 2021 at 09:28:27PM +0800, Keqian Zhu wrote:
The purpose of QEMU commit 65ace0604551 (migration: add postcopy total blocktime into query-migrate) is to query some postcopy related information on destination side.
The total post-copy block time is only computed when postcopy-blocktime migration capability is enabled. Libvirt does not support this capability so I believe this patch is fixing something that can never happen.
We can call query-migrate on destination side *after* migration complete, thanks.
But nothing in libvirt ever tries to call query-migrate on the dest side. Yes, but the dest side does not always act as dest. After migration completion, the dest side enters to a normal status and libvirt does not forbid us to query migration status.
Before QEMU commit 65ace0604551, we can successfully query the migration status, which is MIGRATION_STATUS_NONE. But this commit will return valid status (MIGRATION_STATUS_COMPLETED) without ram info, causing libvirt reports error (migration was active, but no RAM info was set).
Do you have more patches that add such calls ? If so, then please send a patch series that does the full job.
I do not add new feature to libvirt, but just manually execute query-migrate on dest side *after migration completion* will trigger this problem.
How are you running query-migrate ? If you're doing that with monitor command passthrough then we shouldn't need to change the libvirt migration code. OK. I am not very familiar with libvirt code logic, and my work flow is:
source side dest side
virsh start domain_name | | | virsh migrate --live domain_name (wait for migrate complete) | | (migrate complete) | virsh domjobinfo domain_name | (migration was active, but no RAM info was set)
Hope the above work flow helps.
You're trying to fetch statistics about a completed migration, for which virsh domjobinfo --completed should be used. Instead of hacking around it, we should properly implement support for postcopy-blocktime and fetch the blocktime once migration completes internally to make it available via the existing virsh domjobinfo --completed command. Libvirt users should not need to know that domjobinfo may magically be called even when migration is not running to fetch some additional data. Jirka