From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: [PATCH RFC v4 net-next 3/5] virtio-net: optimize free_old_xmit_skbs stats Date: Mon, 1 Dec 2014 18:17:06 +0800 Message-ID: <1417429028-11971-4-git-send-email-jasowang@redhat.com> References: <1417429028-11971-1-git-send-email-jasowang@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: pagupta@redhat.com To: mst@redhat.com, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, davem@davemloft.net Return-path: In-Reply-To: <1417429028-11971-1-git-send-email-jasowang@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org List-Id: netdev.vger.kernel.org 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 Cc: Michael S. Tsirkin Signed-off-by: Jason Wang Signed-off-by: Michael S. Tsirkin --- 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) -- 1.8.3.1