virtio_net: exploit napi_complete_done() return value

Since commit 364b6055738b ("net: busy-poll: return busypolling status to
drivers"), napi_complete_done() returns a boolean that can be used
by drivers to conditionally rearm interrupts.

This patch changes virtio_net to use this boolean to avoid a bit of
overhead for busy-poll users.

Jason reports about 1.1% improvement for 1 byte TCP_RR (burst 100).

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 0382827..29982c7 100644 (file)
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1012,11 +1012,12 @@ static int virtnet_poll(struct napi_struct *napi, int budget)
        /* Out of packets? */
        if (received < budget) {
                r = virtqueue_enable_cb_prepare(rq->vq);
-               napi_complete_done(napi, received);
-               if (unlikely(virtqueue_poll(rq->vq, r)) &&
-                   napi_schedule_prep(napi)) {
-                       virtqueue_disable_cb(rq->vq);
-                       __napi_schedule(napi);
+               if (napi_complete_done(napi, received)) {
+                       if (unlikely(virtqueue_poll(rq->vq, r)) &&
+                           napi_schedule_prep(napi)) {
+                               virtqueue_disable_cb(rq->vq);
+                               __napi_schedule(napi);
+                       }
                }
        }