Re: [Qemu-devel] [regression] dataplane: throughout -40% by commit 580b6b2aa2

[Ming Lei]

On Thu, Jul 3, 2014 at 7:56 PM, Paolo Bonzini <address@hidden> wrote:
> Il 03/07/2014 13:50, Ming Lei ha scritto:
>
>>> Yes, you can just move the atomic_inc/atomic_dec in aio_poll.
>>
>>
>> If you mean move inc/dec of 'running' in aio_poll, that won't work.
>> When aio_notify() sees 'running', it won't set notifier, and may
>> trap to ppoll().
>
>
> I mean move it to aio_poll, around the second invocation of aio_dispatch.
> IIRC the first invocation of aio_dispatch is only used when AioContext is
> running as a GSource.  It should never run for dataplane, so it's okay if we
> only trap aio_notify from the second aio_dispatch().

That is fine.

>
> In 2.2, we should rewrite aio_poll() to follow the
> prepare/poll/check/dispatch model of glib.  Then the optimization becomes
> much simpler (you only call aio_dispatch once) and it also works for GSource
> mode.
>
> Stefan convinced me to send the patch myself, so I will do it now.

That is great, and virtio-blk multi vqs can benefit from this patch
a lot, :-)

Thanks,
-- 
Ming Lei