[RFC PATCH net-next 3/6] virtio-net: small optimization on free_old_xmit_skbs()

Jason Wang
2014-10-15T07:25:27Z

Accumulate the sent packets and sent bytes in local variables and perform a
single u64_stats_update_begin/end() after.

Cc: Rusty Russell <rusty at rustcorp.com.au>
Cc: Michael S. Tsirkin <mst at redhat.com>
Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/net/virtio_net.c |   12 ++++++++----
 1 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 3d0ce44..a4d56b8 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -833,17 +833,21 @@ static void free_old_xmit_skbs(struct send_queue *sq)
 	unsigned int len;
 	struct virtnet_info *vi = sq->vq->vdev->priv;
 	struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
+	u64 tx_bytes = 0, tx_packets = 0;

 	while ((skb = virtqueue_get_buf(sq->vq, &len)) != NULL) {
 		pr_debug("Sent skb %p\n", skb);

-		u64_stats_update_begin(&stats->tx_syncp);
-		stats->tx_bytes += skb->len;
-		stats->tx_packets++;
-		u64_stats_update_end(&stats->tx_syncp);
+		tx_bytes += skb->len;
+		tx_packets++;

 		dev_kfree_skb_any(skb);
 	}
+
+	u64_stats_update_begin(&stats->tx_syncp);
+	stats->tx_bytes += tx_bytes;
+	stats->tx_packets =+ tx_packets;
+	u64_stats_update_end(&stats->tx_syncp);
 }

 static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)
--
1.7.1