Re: [Qemu-devel] [PATCH v5 17/17] migration: Flush receive queue

[Juan Quintela <quintela@redhat.com>]

Peter Xu <peterx@redhat.com> wrote:
> On Mon, Jul 17, 2017 at 03:42:38PM +0200, Juan Quintela wrote:
>> Each time that we sync the bitmap, it is a possiblity that we receive
>> a page that is being processed by a different thread.  We fix this
>> problem just making sure that we wait for all receiving threads to
>> finish its work before we procedeed with the next stage.
>> 
>> We are low on page flags, so we use a combination that is not valid to
>> emit that message:  MULTIFD_PAGE and COMPRESSED.
>
> Btw, would it be possible that we introduce a new QEMU_VM_COMMAND for
> this flush operation?  Like: MIG_CMD_MULTIFD_FLUSH?

>From the commit message:

> I tried to make a migration command for it, but it don't work because
> we sync the bitmap sometimes when we have already sent the beggining
> of the section, so I just added a new page flag.

Yeap, I found that much better dessign, but without further surgery, it
is not trivial.  There are two places where we can sync the bitmap, and
in one of them, we have already sent the beggining of the section, so
too late to send a command.

Later, Juan.