Hello Jiri, On Thursday 29 August, 2024 at 04:58:39 pm IST, Jiri Denemark <jdenemar@xxxxxxxxxx> wrote: >> * Does the same waiting happen when using options (2) and (3) above? > >No. The explicit "virsh migrate-postcopy" request expects the user to >decide when to switch to post-copy by monitoring the migration. > >> * While running migration tests switch to postcopy appears to >> happen within 2 seconds of starting migration. >> - Is that reasonable time to switch from pre-copy to postcopy? > >No, that's not very reasonable. Basically every memory page access would >have to be delayed until the page is transferred from the source host. > >> - Is there an ideal time to wait before switching to postcopy? > >Not really. As the name suggests this is meant as a timeout, i.e., >switch to post-copy if pre-copy migration is taking too long and thus is >unlikely to ever converge. So logically the timeout should be long >enough to give pre-copy migration to do its job. In this case, switching >to post-copy is an alternative approach to CPU throttling for helping >migration to converge. > > >> * The feature page below suggests to wait until one cycle of RAM migration has completed >> -> https://wiki.qemu.org/Features/PostCopyLiveMigration ; > > >Right, that's definitely a good approach as only memory pages that >changed during migration will have to be transferred from the source. > * Okay, great! Thanks so much for these details, I appreciate it. Thank you. --- - Prasad
