[libvirt] [PATCH 6/6] qemu: Allow showing the dump progress for memory only dump

[Jiri Denemark]

On Fri, Nov 17, 2017 at 18:17:31 -0500, John Ferlan wrote:
> https://bugzilla.redhat.com/show_bug.cgi?id=916061
> 
> If the QEMU version running is new enough (based on QEMU_CAPS_QUERY_DUMP)
> we can add a 'detach' boolean to the dump-guest-memory command in order
> to tell QEMU to run in a thread. Then, use the qemuDumpWaitForCompletion
> in order to 'watch' the dump and save the stats into the jobInfo data
> so that tools (such as virsh) can pick up and display the completion
> percentage. The processing is similar to qemuMigrationWaitForCompletion
> at least with respect to calling the query-dump in a while loop that
> gets a micro sleep in order for qemuDomainGetJobInfo to be able to
> pull out the changed migration stats values.

Looks like the code was inspired by our old migration flow with a lot of
copy&paste work. However, I don't think this is necessary. Does QEMU
provide any event when a detached dump completes? If so, we should use
it. If QEMU does not provide the event, I think we should only add
support for detached dump once the event is implemented in QEMU. In
other words, we should never poll for dump progress every 50ms.

Jirka