Hello,
* virsh(1) offers multiple options to initiate Postcopy migration:
1) virsh migrate --postcopy --postcopy-after-precopy
2) virsh migrate --postcopy + virsh migrate-postcopy
3) virsh migrate --postcopy --timeout <N> --timeout-postcopy
When Postcopy migration is invoked via options (2) or (3) above, the migrated
guest on the destination host hangs sometimes. But such a hang is not
reproducible with option (1) above.
* When using option (1) above, libvirtd(8) waits for the first pass of pre-copy
to finish before enabling postcopy migration.
* Does the same waiting happen when using options (2) and (3) above?
===
2024-07-24 14:16:27.448+0000: msg={"execute":"migrate"
2024-07-24 14:16:29.318+0000: msg={"execute":"migrate-start-postcopy"
2024-07-24 14:28:39.737+0000: msg={"execute":"migrate"
2024-07-24 14:28:41.119+0000: msg={"execute":"migrate-start-postcopy"
2024-07-24 14:44:11.684+0000: msg={"execute":"migrate"
2024-07-24 14:44:12.835+0000: msg={"execute":"migrate-start-postcopy"
2024-07-24 14:48:00.675+0000: msg={"execute":"migrate"
2024-07-24 14:48:02.319+0000: msg={"execute":"migrate-start-postcopy"
2024-07-24 15:03:36.110+0000: msg={"execute":"migrate"
2024-07-24 15:03:37.341+0000: msg={"execute":"migrate-start-postcopy"
2024-07-24 16:05:25.602+0000: msg={"execute":"migrate"
2024-07-24 16:05:26.756+0000: msg={"execute":"migrate-start-postcopy"
===
* While running migration tests with options (2) and (3) above, switch to
postcopy appears to happen within 2 seconds of starting migration.
- Is that reasonable time to switch from pre-copy to postcopy?
- Is there an ideal time to wait before switching to postcopy?
* The feature page below suggests to wait until one cycle of RAM migration has
completed
-> https://wiki.qemu.org/Features/PostCopyLiveMigration
* I'd much appreciate any clarification/confirmation about this.
Thank you.
---
-Prasad
