Avihai Horon <avih...@nvidia.com> wrote: > 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 > migration users. 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 "precopy initial data" that allows the > source to send initial precopy data and the destination to ACK that this > data has been loaded. Migration will not attempt to stop the source VM > and complete the migration until this ACK is received. > > This will allow migration users to send initial precopy data which can > be used to reduce downtime (e.g., by pre-allocating resources), while > making sure that the source will stop the VM and complete the migration > only after this initial precopy data is sent and loaded in the > destination 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 <avih...@nvidia.com>
Capability definition is correct. I am not given the review-by until the rest of the series is discussed, but nothing else to do here.
