Commit 663e6c1d authored Nov 05, 2015 by Dr. David Alan Gilbert Committed by Juan Quintela Nov 10, 2015

Don't sync dirty bitmaps in postcopy



Once we're in postcopy the source processors are stopped and memory
shouldn't change any more, so there's no need to look at the dirty
map.

There are two notes to this:
  1) If we do resync and a page had changed then the page would get
     sent again, which the destination wouldn't allow (since it might
     have also modified the page)
  2) Before disabling this I'd seen very rare cases where a page had been
     marked dirtied although the memory contents are apparently identical

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

parent c53b7ddc

migration/ram.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -1846,7 +1846,9 @@ static int ram_save_complete(QEMUFile f, void opaque)
		{
		rcu_read_lock();

		if (!migration_in_postcopy(migrate_get_current())) {
		migration_bitmap_sync();
		}

		ram_control_before_iterate(f, RAM_CONTROL_FINISH);

		@@ -1881,7 +1883,8 @@ static void ram_save_pending(QEMUFile f, void opaque, uint64_t max_size,

		remaining_size = ram_save_remaining() * TARGET_PAGE_SIZE;

		if (remaining_size < max_size) {
		if (!migration_in_postcopy(migrate_get_current()) &&
		remaining_size < max_size) {
		qemu_mutex_lock_iothread();
		rcu_read_lock();
		migration_bitmap_sync();