Re: [Qemu-devel] [PATCH 2/2] virtio-blk: dataplane: notify guest as a batch

[Ming Lei]

On Fri, Jul 4, 2014 at 11:48 PM, Paolo Bonzini <address@hidden> wrote:
> Il 04/07/2014 16:52, Ming Lei ha scritto:
>
>>> > What you can do is change notify_guest to something like
>>> >
>>> >     qemu_bh_schedule(req->dev->dataplane->notify_guest_bh);
>>> >
>>> > and do the actual notification in the bottom half.  This should ensure
>>> > that
>>> > multiple notifications are coalesced, but it may also introduce new
>>> > aio_notify calls even with my patch (a BH scheduled from a BH currently
>>> > does
>>> > an aio_notify; this can be fixed).
>>
>> I think we can do better than above because one aio IO completes lots of
>> requests, and we just need to notify guest for all these requests.
>
>
> Exactly, there would be just one BH and thus just one notify.

But we have two cases to consider:

- one submitted IO includes requests from multi vq(virtio-blk or
virtio-scsi maybe),
and each vq has to notify guest

- one submitted IO includes requests from multi bs for scsi device

The 2nd case should be easy to handle, but I am a bit headache for the 1st case.



Thanks,
--
Ming Lei