Commit 90697be8 authored by Jan Kiszka's avatar Jan Kiszka Committed by Anthony Liguori
Browse files

live migration: Serialize vmstate saving in stage 2 



The effect of this patch with current block migration is that its stage
2, ie. the first full walk-through of the block devices will be
performed completely before RAM migration starts. This ensures that
continuously changing RAM pages are not re-synchronized all the time
while block migration is not completed.

Future versions of block migration which will respect the specified
downtime will generate a different pattern: After RAM migration has
started as well, block migration may also continue to inject dirty
blocks into the RAM stream once it detects that the number of pending
blocks would extend the downtime unacceptably.

Note that all this relies on the current registration order: block
before RAM migration.

Signed-off-by: default avatarJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: default avatarAnthony Liguori <aliguori@us.ibm.com>
parent 792773b2

savevm.c

+8 −1
Original line number Diff line number Diff line
@@ -1321,7 +1321,14 @@ int qemu_savevm_state_iterate(Monitor *mon, QEMUFile *f) 
        qemu_put_byte(f, QEMU_VM_SECTION_PART);

        qemu_put_be32(f, se->section_id);



        ret &= !!se->save_live_state(mon, f, QEMU_VM_SECTION_PART, se->opaque);

        ret = se->save_live_state(mon, f, QEMU_VM_SECTION_PART, se->opaque);

        if (!ret) {

            /* Do not proceed to the next vmstate before this one reported

               completion of the current stage. This serializes the migration

               and reduces the probability that a faster changing state is

               synchronized over and over again. */

            break;

        }

    }



    if (ret)