[Qemu-devel] Re: [PATCH v3 0/5] Add QMP migration events

[Juan Quintela <quintela@redhat.com>]

Anthony Liguori <anthony@codemonkey.ws> wrote:
> On 06/14/2010 02:54 PM, Juan Quintela wrote:
>> Anthony Liguori<aliguori@linux.vnet.ibm.com>  wrote:

>>> What makes migration important and not savevm?
>>>      
>> That is the reason why I insist to have the events "both" in source and
>> destination.  About how to integrate savevm on the whole picture ....
>>
>> VM_SAVE_START/VM_SAVE_END/VM_RESTORE_START/VM_RESTORE_END events?
>>    
>
> If savevm is an asychronous command, then it's already there.
>
> You really want to support turning all command submissions/completions
> into events.   You could do it with two events.  The first would be
> COMMAND_REQUEST and would contain the request data and which monitor
> it occurred on.  The second would be COMMAND_RESPONSE and would
> contain the response data and which monitor it occurred on.
>
> But honestly, I think it's a stretch to say this functionality is
> really needed.

As already told, what I need is the migration ones.

The imporant case is MIGRATION_ENDED on target when migration were
sucessful.  This is the fast path, and it makes a difference here.

MIGRATION_STARTED on target is also quite "nice" to have.  At this point
libvirt has an

sleep(250ms): echo "cont"

Due to a race here in incoming migration.

As we only wanted one ending event, can agree on:

MIGRATION_STARTED(both source and target)
MIGRATION_DONE(result) (both source and target)

where result can be ok or -1 (at this point we don't have anything else
to put there).

That moves us from 4 events to 2?

Later, Juan.