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@redhat.com> --- 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 also wonder if we should add a code that will error out if it's not the case, currently it would be silently ignored.
+ * + * Since: 10.9.0 + */ +# define VIR_MIGRATE_PARAM_MIGRATE_DISKS_DETECT_ZEROES "migrate_disks_detect_zeroes" + /** * VIR_MIGRATE_PARAM_DISKS_PORT: *
[...]
diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c index 94636e778d..7ae19dd0ce 100644 --- a/src/qemu/qemu_migration.c +++ b/src/qemu/qemu_migration.c @@ -5316,9 +5348,11 @@ qemuMigrationSrcPerformTunnel(virQEMUDriver *driver, goto cleanup; }
+ /* Migration with NBD is not supported with _TUNNELED, thus
s/_TUNNELED/_TUNNELLED/ To match the incorrect spelling of the actual flag.
+ * 'migrate_disks_detect_zeroes' is NULL here */ ret = qemuMigrationSrcRun(driver, vm, xmlin, persist_xml, cookiein, cookieinlen, cookieout, cookieoutlen, flags, resource, &spec, - dconn, graphicsuri, migrate_disks, + dconn, graphicsuri, migrate_disks, NULL, migParams, NULL);
cleanup:
Pavel