* Wei Wang (address@hidden) wrote:
The new feature enables the virtio-balloon device to receive hints of
guest free pages from the free page vq.
A notifier is registered to the migration precopy notifier chain. The
notifier calls free_page_start after the migration thread syncs the dirty
bitmap, so that the free page optimization starts to clear bits of free
pages from the bitmap. It calls the free_page_stop before the migration
thread syncs the bitmap, which is the end of the current round of ram
save. The free_page_stop is also called to stop the optimization in the
case when there is an error occurred in the process of ram saving.
Note: balloon will report pages which were free at the time of this call.
As the reporting happens asynchronously, dirty bit logging must be
enabled before this free_page_start call is made. Guest reporting must be
disabled before the migration dirty bitmap is synchronized.
Signed-off-by: Wei Wang <address@hidden>
CC: Michael S. Tsirkin <address@hidden>
CC: Dr. David Alan Gilbert <address@hidden>
CC: Juan Quintela <address@hidden>
CC: Peter Xu <address@hidden>
I think I'm OK for this from the migration side, I'd appreciate
someone checking the virtio and aio bits.
I'm not too sure how it gets switched on and off - i.e. if we get a nice
new qemu on a new kernel, what happens when I try and migrate to the
same qemu on an older kernel without these hints?