About virsh(1) and Postcopy migration

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