[Qemu-devel] Re: [PATCH 22/22] migration: Make state definitions local

[Juan Quintela <quintela@redhat.com>]

Yoshiaki Tamura <tamura.yoshiaki@lab.ntt.co.jp> wrote:
> 2011/2/23 Juan Quintela <quintela@redhat.com>:
>> Yoshiaki Tamura <tamura.yoshiaki@lab.ntt.co.jp> wrote:
>>> 2011/2/23 Juan Quintela <quintela@redhat.com>:

>>> Although you're right, I would prefer to keep it so that somebody
>>> outside of migration may understand the status in the future if
>>> there are no harms.
>>
>> my plan is to move MigrationState inside migration.c, and then decide
>> what to export/not export.
>
> Well, it may be just a policy, but it's already exported, and I
> would like to keep it unless it bothers your plan.  IIUC, I don't
> think it does.
>
>> Next thing to do is move migration to its
>> own thread.  Before doing that, I need to know what parts are used/not
>> used outside migration.c.  Removing it now means that nothing gets to
>> use it without needing a patch.
>
> I've once asked Anthony whether it's possible to make migration
> to different threads, but his answer was no due to hard
> dependency of qemu's internal code, and making migration to
> different threads are bad design.

I know.  But Anthony is seeing the light O:-)

Basically, without an own thread we are not able to:
- do anything else while on incoming migration
  (namely using the monitor)
- do anything else than migration.  We can try hard and let vcpus to
  run, but we would still clog the io_thread.
- We are not able to saturate 10Gbit networking (basically we are doing
  2/3 level of bufferering (depending on how you count).

So, once code is there, I guess we will convince Anthony to commit it.

Later, Juan.