[Qemu-devel] frame reordering in qemu_net_queue_send() ?

[Luigi Rizzo]

Hi,
while investigating rx performance for emulated network devices
(i am looking at the userspace version, relying on net=tap
or similar approaches) i noticed the code
in net/queue.c :: qemu_net_queue_send()
which look strange to me (same goes for the iov version).

The whole function is below, just for reference.
My impression is that the call to qemu_net_queue_flush()
is misplaced, and it should be before qemu_net_queue_deliver()
otherwise the current packet is pushed out before anything
was already in the queue.

Does it make sense ?

cheers
luigi

    ssize_t qemu_net_queue_send(NetQueue *queue,
                                VLANClientState *sender,
                                unsigned flags,
                                const uint8_t *data,
                                size_t size,
                                NetPacketSent *sent_cb)
    {
        ssize_t ret;

        if (queue->delivering) {
            return qemu_net_queue_append(queue, sender, flags, data, size, 
NULL);
        }

        ret = qemu_net_queue_deliver(queue, sender, flags, data, size);
        if (ret == 0) {
            qemu_net_queue_append(queue, sender, flags, data, size, sent_cb);
            return 0;
        }

        qemu_net_queue_flush(queue);
    
        return ret;
    }