From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751899AbbEYFY3 (ORCPT ); Mon, 25 May 2015 01:24:29 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57164 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751785AbbEYFY0 (ORCPT ); Mon, 25 May 2015 01:24:26 -0400 From: Jason Wang To: mst@redhat.com, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org Cc: rusty@rustcorp.com.au, Jason Wang Subject: [RFC V7 PATCH 3/7] virtio-net: optimize free_old_xmit_skbs stats Date: Mon, 25 May 2015 01:24:00 -0400 Message-Id: <1432531444-50193-4-git-send-email-jasowang@redhat.com> In-Reply-To: <1432531444-50193-1-git-send-email-jasowang@redhat.com> References: <1432531444-50193-1-git-send-email-jasowang@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@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 | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 63c7810..744f0b1 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -826,17 +826,27 @@ 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, 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) -- 1.8.3.1