From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: [RFC PATCH net-next 6/6] virtio-net: enable tx interrupt only for the final skb in the chain Date: Wed, 15 Oct 2014 15:25:30 +0800 Message-ID: <1413357930-45302-7-git-send-email-jasowang@redhat.com> References: <1413357930-45302-1-git-send-email-jasowang@redhat.com> Cc: davem@davemloft.net, eric.dumazet@gmail.com, Jason Wang To: rusty@rustcorp.com.au, mst@redhat.com, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org Return-path: In-Reply-To: <1413357930-45302-1-git-send-email-jasowang@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org With the help of xmit_more and virtqueue_enable_cb_avail(), this patch enable tx interrupt only for the final skb in the chain if needed. This will help to mitigate tx interrupts. Cc: Rusty Russell Cc: Michael S. Tsirkin Signed-off-by: Jason Wang --- drivers/net/virtio_net.c | 10 +++++++--- 1 files changed, 7 insertions(+), 3 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 2afc2e2..5943f3f 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -993,12 +993,16 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) virtqueue_disable_cb(sq->vq); } } - } else if (virtqueue_enable_cb(sq->vq)) { - free_old_xmit_skbs(sq, qsize); } - if (__netif_subqueue_stopped(dev, qnum) || !skb->xmit_more) + if (__netif_subqueue_stopped(dev, qnum) || !skb->xmit_more) { virtqueue_kick(sq->vq); + if (sq->vq->num_free >= 2 +MAX_SKB_FRAGS && + unlikely(virtqueue_enable_cb_avail(sq->vq))) { + free_old_xmit_skbs(sq, qsize); + virtqueue_disable_cb(sq->vq); + } + } return NETDEV_TX_OK; } -- 1.7.1