diff options
| author | Avihai Horon <avihaih@nvidia.com> | 2023-06-21 14:11:54 +0300 |
|---|---|---|
| committer | Cédric Le Goater <clg@redhat.com> | 2023-06-30 06:02:51 +0200 |
| commit | 6574232fff6a810e1882c98aa7dcf23d6afe9a31 (patch) | |
| tree | 9763e011369ec71e4fd094336eba441d25940351 /qapi | |
| parent | 4d541f63e90c81112c298cbb35ed53e9c79deb00 (diff) | |
migration: Add switchover ack capability
Migration downtime estimation is calculated based on bandwidth and
remaining migration data. This assumes that loading of migration data in
the destination takes a negligible amount of time and that downtime
depends only on network speed.
While this may be true for RAM, it's not necessarily true for other
migrated devices. For example, loading the data of a VFIO device in the
destination might require from the device to allocate resources, prepare
internal data structures and so on. These operations can take a
significant amount of time which can increase migration downtime.
This patch adds a new capability "switchover ack" that prevents the
source from stopping the VM and completing the migration until an ACK
is received from the destination that it's OK to do so.
This can be used by migrated devices in various ways to reduce downtime.
For example, a device can send initial precopy metadata to pre-allocate
resources in the destination and use this capability to make sure that
the pre-allocation is completed before the source VM is stopped, so it
will have full effect.
This new capability relies on the return path capability to communicate
from the destination back to the source.
The actual implementation of the capability will be added in the
following patches.
Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Tested-by: YangHang Liu <yanghliu@redhat.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Diffstat (limited to 'qapi')
| -rw-r--r-- | qapi/migration.json | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/qapi/migration.json b/qapi/migration.json index 5bb5ab82a0..47dfef0278 100644 --- a/qapi/migration.json +++ b/qapi/migration.json @@ -487,6 +487,16 @@ # and should not affect the correctness of postcopy migration. # (since 7.1) # +# @switchover-ack: If enabled, migration will not stop the source VM +# and complete the migration until an ACK is received from the +# destination that it's OK to do so. Exactly when this ACK is +# sent depends on the migrated devices that use this feature. +# For example, a device can use it to make sure some of its data +# is sent and loaded in the destination before doing switchover. +# This can reduce downtime if devices that support this capability +# are present. 'return-path' capability must be enabled to use +# it. (since 8.1) +# # Features: # # @unstable: Members @x-colo and @x-ignore-shared are experimental. @@ -502,7 +512,7 @@ 'dirty-bitmaps', 'postcopy-blocktime', 'late-block-activate', { 'name': 'x-ignore-shared', 'features': [ 'unstable' ] }, 'validate-uuid', 'background-snapshot', - 'zero-copy-send', 'postcopy-preempt'] } + 'zero-copy-send', 'postcopy-preempt', 'switchover-ack'] } ## # @MigrationCapabilityStatus: |