[PATCH RFC v4 net-next 3/5] virtio-net: optimize free_old_xmit_skbs stats
From: Jason Wang <jasowang@redhat.com>
Date: 2014-12-01 10:17:30
Also in:
lkml, virtualization
Subsystem:
networking drivers, the rest, virtio net driver · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, "Michael S. Tsirkin", Jason Wang
We already have counters for sent packets and sent bytes. Use them to reduce the number of u64_stats_update_begin/end(). Take care not to bother with stats update when called speculatively. Cc: Rusty Russell <redacted> Cc: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Jason Wang <jasowang@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> --- drivers/net/virtio_net.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 0ed24ff..9f420c9 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c@@ -230,16 +230,23 @@ static unsigned int free_old_xmit_skbs(struct netdev_queue *txq, (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; bytes += skb->len; - stats->tx_packets++; - u64_stats_update_end(&stats->tx_syncp); + packets++; dev_kfree_skb_any(skb); - packets++; } + /* Avoid overhead when no packets have been processed + * happens when called speculatively from start_xmit. + */ + if (!packets) + return 0; + + u64_stats_update_begin(&stats->tx_syncp); + stats->tx_bytes += bytes; + stats->tx_packets += packets; + u64_stats_update_end(&stats->tx_syncp); + netdev_tx_completed_queue(txq, packets, bytes); if (sq->vq->num_free >= 2+MAX_SKB_FRAGS)
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1.8.3.1