Re: [PATCH v3 3/3] multifd: Send using asynchronous write on nocomp to send RAM pages.

[Leonardo Bras Soares Passos <leobras@redhat.com>]

On Tue, Sep 28, 2021 at 7:49 PM Peter Xu <peterx@redhat.com> wrote:
>
> On Fri, Sep 24, 2021 at 06:43:49PM +0100, Daniel P. Berrangé wrote:
> > > @@ -546,6 +546,7 @@ void multifd_save_cleanup(void)
> > >          MultiFDSendParams *p = &multifd_send_state->params[i];
> > >          Error *local_err = NULL;
> > >
> > > +        qio_channel_async_flush(p->c, NULL);
> > >          socket_send_channel_destroy(p->c);
> > >          p->c = NULL;
> > >          qemu_mutex_destroy(&p->mutex);
> >
> > This isn't reliable beucase qio_channel_async_flush will return early
> > even if not everything is flushed.
>
> Right, though I think the problem is in patch 2 where we should make sure
> flush() will only return if all data sent.
>
> And at the meantime we may also want to move it to before we send the devices
> states for both pre/post copy.  multifd_save_cleanup() is called only until
> migration completed and we're cleaning stuffs, I'm afraid it's too late, so
> potentially the device states can arrive and dest vm running without the latest
> src VM memories.

Thanks for that Peter!
I had some trouble sorting out when to flush, and I think I still missed this.

I will have thet improved for v3.

>
> --
> Peter Xu
>

Best regards,
Leonardo