Has return zero for more than 10 years.
Specifically we introduced the field in 1.5.0
commit f1c72795af
Author: Peter Lieven <pl@kamp.de>
Date: Tue Mar 26 10:58:37 2013 +0100
migration: do not sent zero pages in bulk stage
during bulk stage of ram migration if a page is a
zero page do not send it at all.
the memory at the destination reads as zero anyway.
even if there is an madvise with QEMU_MADV_DONTNEED
at the target upon receipt of a zero page I have observed
that the target starts swapping if the memory is overcommitted.
it seems that the pages are dropped asynchronously.
this patch also updates QMP to return the number of
skipped pages in MigrationStats.
but removed its usage in 1.5.3
commit 9ef051e553
Author: Peter Lieven <pl@kamp.de>
Date: Mon Jun 10 12:14:19 2013 +0200
Revert "migration: do not sent zero pages in bulk stage"
Not sending zero pages breaks migration if a page is zero
at the source but not at the destination. This can e.g. happen
if different BIOS versions are used at source and destination.
It has also been reported that migration on pseries is completely
broken with this patch.
This effectively reverts commit f1c72795af.
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-ID: <20230612193344.3796-2-quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
7b24d32634