We already have counters for sent/recv packets and sent/recv bytes.
Doing a batched update to reduce the number of
u64_stats_update_begin/end().
Take care not to bother with stats update when called
speculatively.
Cc: Willem de Bruijn <willemb at google.com>
Signed-off-by: Jason Wang <jasowang at redhat.com>
Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
---
drivers/net/virtio_net.c | 47 +++++++++++++++++++++++++++++++----------------
1 file changed, 31 insertions(+), 16 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 11e2853..05a83db 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -719,13 +719,13 @@ static struct sk_buff *receive_mergeable(struct net_device
*dev,
return NULL;
}
-static void receive_buf(struct virtnet_info *vi, struct receive_queue *rq,
- void *buf, unsigned int len)
+static int receive_buf(struct virtnet_info *vi, struct receive_queue *rq,
+ void *buf, unsigned int len)
{
struct net_device *dev = vi->dev;
- struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
struct sk_buff *skb;
struct virtio_net_hdr_mrg_rxbuf *hdr;
+ int ret;
if (unlikely(len < vi->hdr_len + ETH_HLEN)) {
pr_debug("%s: short packet %i\n", dev->name, len);
@@ -739,7 +739,7 @@ static void receive_buf(struct virtnet_info *vi, struct
receive_queue *rq,
} else {
dev_kfree_skb(buf);
}
- return;
+ return 0;
}
if (vi->mergeable_rx_bufs)
@@ -750,14 +750,11 @@ static void receive_buf(struct virtnet_info *vi, struct
receive_queue *rq,
skb = receive_small(dev, vi, rq, buf, len);
if (unlikely(!skb))
- return;
+ return 0;
hdr = skb_vnet_hdr(skb);
- u64_stats_update_begin(&stats->rx_syncp);
- stats->rx_bytes += skb->len;
- stats->rx_packets++;
- u64_stats_update_end(&stats->rx_syncp);
+ ret = skb->len;
if (hdr->hdr.flags & VIRTIO_NET_HDR_F_DATA_VALID)
skb->ip_summed = CHECKSUM_UNNECESSARY;
@@ -775,11 +772,12 @@ static void receive_buf(struct virtnet_info *vi, struct
receive_queue *rq,
ntohs(skb->protocol), skb->len, skb->pkt_type);
napi_gro_receive(&rq->napi, skb);
- return;
+ return ret;
frame_err:
dev->stats.rx_frame_errors++;
dev_kfree_skb(skb);
+ return 0;
}
static unsigned int virtnet_get_headroom(struct virtnet_info *vi)
@@ -994,12 +992,13 @@ static void refill_work(struct work_struct *work)
static int virtnet_receive(struct receive_queue *rq, int budget)
{
struct virtnet_info *vi = rq->vq->vdev->priv;
- unsigned int len, received = 0;
+ unsigned int len, received = 0, bytes = 0;
void *buf;
+ struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
while (received < budget &&
(buf = virtqueue_get_buf(rq->vq, &len)) != NULL) {
- receive_buf(vi, rq, buf, len);
+ bytes += receive_buf(vi, rq, buf, len);
received++;
}
@@ -1008,6 +1007,11 @@ static int virtnet_receive(struct receive_queue *rq, int
budget)
schedule_delayed_work(&vi->refill, 0);
}
+ u64_stats_update_begin(&stats->rx_syncp);
+ stats->rx_bytes += bytes;
+ stats->rx_packets += received;
+ u64_stats_update_end(&stats->rx_syncp);
+
return received;
}
@@ -1056,17 +1060,28 @@ 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);
+ unsigned int packets = 0;
+ unsigned int bytes = 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);
+ bytes += skb->len;
+ packets++;
dev_kfree_skb_any(skb);
}
+
+ /* Avoid overhead when no packets have been processed
+ * happens when called speculatively from start_xmit.
+ */
+ if (!packets)
+ return;
+
+ u64_stats_update_begin(&stats->tx_syncp);
+ stats->tx_bytes += bytes;
+ stats->tx_packets += packets;
+ u64_stats_update_end(&stats->tx_syncp);
}
static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)
--
2.7.4
