From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: [PATCH RFC v3 3/3] virtio-net: optimize free_old_xmit_skbs stats Date: Mon, 20 Oct 2014 09:52:41 +0300 Message-ID: <1413787824-16130-4-git-send-email-mst@redhat.com> References: <1413787824-16130-1-git-send-email-mst@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jason Wang , Rusty Russell , virtualization@lists.linux-foundation.org, netdev@vger.kernel.org To: linux-kernel@vger.kernel.org, netdev@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:43995 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752484AbaJTGtL (ORCPT ); Mon, 20 Oct 2014 02:49:11 -0400 Content-Disposition: inline In-Reply-To: <1413787824-16130-1-git-send-email-mst@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: From: 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. Based on a patch by Jason Wang. Cc: Rusty Russell Signed-off-by: Jason Wang Signed-off-by: Michael S. Tsirkin --- drivers/net/virtio_net.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index b83d39d..c2b69f8 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -233,16 +233,22 @@ 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) -- MST