Re: [PATCH 12/13] qemu: Introduce and wire in 'VIR_MIGRATE_PARAM_MIGRATE_DISKS_DETECT_ZEROES'

On Mon, Sep 30, 2024 at 16:53:55 +0200, Pavel Hrdina wrote: > On Mon, Sep 30, 2024 at 03:29:34PM +0200, Peter Krempa wrote: > > The new 'VIR_MIGRATE_PARAM_MIGRATE_DISKS_DETECT_ZEROES' migration > > parameter allows users of migration to pass in a list of disks where > > zero-detection (which avoids transferring the zeroed-blocks) should be > > enabled for the migration connection. This comes at the cost of extra > > CPU cycles needed to check each block if it's all-zero. > > > > This is useful for storage backends where information about the > > allocation state of a block is not available and thus without this the > > image would become fully allocated on the destination. > > > > Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; > > --- > > include/libvirt/libvirt-domain.h | 13 ++++ > > src/qemu/qemu_driver.c | 20 ++++-- > > src/qemu/qemu_migration.c | 105 +++++++++++++++++++++++-------- > > src/qemu/qemu_migration.h | 4 ++ > > 4 files changed, 110 insertions(+), 32 deletions(-) > > > > diff --git a/include/libvirt/libvirt-domain.h b/include/libvirt/libvirt-domain.h > > index 4266237abe..6d4cc69c5d 100644 > > --- a/include/libvirt/libvirt-domain.h > > +++ b/include/libvirt/libvirt-domain.h > > @@ -1240,6 +1240,19 @@ typedef enum { > > */ > > # define VIR_MIGRATE_PARAM_MIGRATE_DISKS "migrate_disks" > > > > +/** > > + * VIR_MIGRATE_PARAM_MIGRATE_DISKS_DETECT_ZEROES: > > + * > > + * virDomainMigrate* params multiple field: The multiple values that list > > + * the block devices for which zero detection (to avoid transferring zero blocks) > > + * is to be enabled. This may increase CPU overhead of the migration. At the > > + * moment this is only supported by the QEMU driver but not for the tunnelled > > + * migration. > > We should note that it has to be subset of migrate_disks values. I'd argue that it's logical that this can apply only if the disk is being migrated.