Re: [Qemu-devel] [PATCH 1/3] net: notify iothread after flushing queue

[Blue Swirl]

On Thu, Aug 9, 2012 at 2:45 PM, Paolo Bonzini <address@hidden> wrote:
> virtio-net has code to flush the queue and notify the iothread
> whenever new receive buffers are added by the guest.  That is
> fine, and indeed we need to do the same in all other drivers.
> However, notifying the iothread should be work for the network
> subsystem.  And since we are at it we can add a little smartness:
> if some of the queued packets already could not be delivered,
> there is no need to notify the iothread.
>
> Reported-by: Luigi Rizzo <address@hidden>
> Cc: Stefan Hajnoczi <address@hidden>
> Cc: Jan Kiszka <address@hidden>
> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
>  hw/virtio-net.c | 4 ----
>  net.c           | 7 ++++++-
>  net/queue.c     | 5 +++--
>  net/queue.h     | 2 +-
>  4 file modificati, 10 inserzioni(+), 8 rimozioni(-)
>
> diff --git a/hw/virtio-net.c b/hw/virtio-net.c
> index b1998b2..6490743 100644
> --- a/hw/virtio-net.c
> +++ b/hw/virtio-net.c
> @@ -447,10 +447,6 @@ static void virtio_net_handle_rx(VirtIODevice *vdev, 
> VirtQueue *vq)
>      VirtIONet *n = to_virtio_net(vdev);
>
>      qemu_flush_queued_packets(&n->nic->nc);
> -
> -    /* We now have RX buffers, signal to the IO thread to break out of the
> -     * select to re-poll the tap file descriptor */
> -    qemu_notify_event();
>  }
>
>  static int virtio_net_can_receive(NetClientState *nc)
> diff --git a/net.c b/net.c
> index 60043dd..76a8336 100644
> --- a/net.c
> +++ b/net.c
> @@ -357,7 +357,12 @@ void qemu_flush_queued_packets(NetClientState *nc)
>  {
>      nc->receive_disabled = 0;
>
> -    qemu_net_queue_flush(nc->send_queue);
> +    if (qemu_net_queue_flush(nc->send_queue)) {
> +        /* We emptied the queue successfully, signal to the IO thread to 
> repoll
> +         * the file descriptor (for tap, for example).
> +         */
> +        qemu_notify_event();
> +    }
>  }
>
>  static ssize_t qemu_send_packet_async_with_flags(NetClientState *sender,
> diff --git a/net/queue.c b/net/queue.c
> index e8030aa..f3f0098 100644
> --- a/net/queue.c
> +++ b/net/queue.c
> @@ -228,7 +228,7 @@ void qemu_net_queue_purge(NetQueue *queue, NetClientState 
> *from)
>      }
>  }
>
> -void qemu_net_queue_flush(NetQueue *queue)
> +bool qemu_net_queue_flush(NetQueue *queue)
>  {
>      while (!QTAILQ_EMPTY(&queue->packets)) {
>          NetPacket *packet;
> @@ -244,7 +244,7 @@ void qemu_net_queue_flush(NetQueue *queue)
>                                       packet->size);
>          if (ret == 0) {
>              QTAILQ_INSERT_HEAD(&queue->packets, packet, entry);
> -            break;
> +            return 0;

return false;

>          }
>
>          if (packet->sent_cb) {
> @@ -253,4 +253,5 @@ void qemu_net_queue_flush(NetQueue *queue)
>
>          g_free(packet);
>      }
> +    return 1;

return true;

>  }
> diff --git a/net/queue.h b/net/queue.h
> index 9d44a9b..fc02b33 100644
> --- a/net/queue.h
> +++ b/net/queue.h
> @@ -53,6 +53,6 @@ ssize_t qemu_net_queue_send_iov(NetQueue *queue,
>                                  NetPacketSent *sent_cb);
>
>  void qemu_net_queue_purge(NetQueue *queue, NetClientState *from);
> -void qemu_net_queue_flush(NetQueue *queue);
> +bool qemu_net_queue_flush(NetQueue *queue);
>
>  #endif /* QEMU_NET_QUEUE_H */
> --
> 1.7.11.2
>
>
>