From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: [RFC PATCH net-next 5/6] virtio-net: enable tx interrupt Date: Wed, 15 Oct 2014 15:25:29 +0800 Message-ID: <1413357930-45302-6-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 Orphan skb in ndo_start_xmit() breaks socket accounting and packet queuing. This in fact breaks lots of things such as pktgen and several TCP optimizations. And also make BQL can't be implemented for virtio-net. This patch tries to solve this issue by enabling tx interrupt. To avoid introducing extra spinlocks, a tx napi was scheduled to free those packets. More tx interrupt mitigation method could be used on top. Cc: Rusty Russell Cc: Michael S. Tsirkin Signed-off-by: Jason Wang --- drivers/net/virtio_net.c | 125 +++++++++++++++++++++++++++++++--------------- 1 files changed, 85 insertions(+), 40 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index ccf98f9..2afc2e2 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -72,6 +72,8 @@ struct send_queue { /* Name of the send queue: output.$index */ char name[40]; + + struct napi_struct napi; }; /* Internal representation of a receive virtqueue */ @@ -217,15 +219,40 @@ static struct page *get_a_page(struct receive_queue *rq, gfp_t gfp_mask) return p; } +static int free_old_xmit_skbs(struct send_queue *sq, int budget) +{ + struct sk_buff *skb; + unsigned int len; + struct virtnet_info *vi = sq->vq->vdev->priv; + struct virtnet_stats *stats = this_cpu_ptr(vi->stats); + u64 tx_bytes = 0, tx_packets = 0; + + while (tx_packets < budget && + (skb = virtqueue_get_buf(sq->vq, &len)) != NULL) { + pr_debug("Sent skb %p\n", skb); + + tx_bytes += skb->len; + tx_packets++; + + dev_kfree_skb_any(skb); + } + + u64_stats_update_begin(&stats->tx_syncp); + stats->tx_bytes += tx_bytes; + stats->tx_packets =+ tx_packets; + u64_stats_update_end(&stats->tx_syncp); + + return tx_packets; +} + static void skb_xmit_done(struct virtqueue *vq) { struct virtnet_info *vi = vq->vdev->priv; + struct send_queue *sq = &vi->sq[vq2txq(vq)]; - /* Suppress further interrupts. */ - virtqueue_disable_cb(vq); - - /* We were probably waiting for more output buffers. */ - netif_wake_subqueue(vi->dev, vq2txq(vq)); + if (napi_schedule_prep(&sq->napi)) { + __napi_schedule(&sq->napi); + } } static unsigned int mergeable_ctx_to_buf_truesize(unsigned long mrg_ctx) @@ -774,7 +801,39 @@ again: return received; } +static int virtnet_poll_tx(struct napi_struct *napi, int budget) +{ + struct send_queue *sq = + container_of(napi, struct send_queue, napi); + struct virtnet_info *vi = sq->vq->vdev->priv; + struct netdev_queue *txq = netdev_get_tx_queue(vi->dev, vq2txq(sq->vq)); + unsigned int r, sent = 0; + +again: + __netif_tx_lock(txq, smp_processor_id()); + virtqueue_disable_cb(sq->vq); + sent += free_old_xmit_skbs(sq, budget - sent); + + if (sent < budget) { + r = virtqueue_enable_cb_prepare(sq->vq); + napi_complete(napi); + __netif_tx_unlock(txq); + if (unlikely(virtqueue_poll(sq->vq, r)) && + napi_schedule_prep(napi)) { + virtqueue_disable_cb(sq->vq); + __napi_schedule(napi); + goto again; + } + } else { + __netif_tx_unlock(txq); + } + + netif_wake_subqueue(vi->dev, vq2txq(sq->vq)); + return sent; +} + #ifdef CONFIG_NET_RX_BUSY_POLL + /* must be called with local_bh_disable()d */ static int virtnet_busy_poll(struct napi_struct *napi) { @@ -822,36 +881,12 @@ static int virtnet_open(struct net_device *dev) if (!try_fill_recv(&vi->rq[i], GFP_KERNEL)) schedule_delayed_work(&vi->refill, 0); virtnet_napi_enable(&vi->rq[i]); + napi_enable(&vi->sq[i].napi); } return 0; } -static int free_old_xmit_skbs(struct send_queue *sq) -{ - struct sk_buff *skb; - unsigned int len; - struct virtnet_info *vi = sq->vq->vdev->priv; - struct virtnet_stats *stats = this_cpu_ptr(vi->stats); - u64 tx_bytes = 0, tx_packets = 0; - - while ((skb = virtqueue_get_buf(sq->vq, &len)) != NULL) { - pr_debug("Sent skb %p\n", skb); - - tx_bytes += skb->len; - tx_packets++; - - dev_kfree_skb_any(skb); - } - - u64_stats_update_begin(&stats->tx_syncp); - stats->tx_bytes += tx_bytes; - stats->tx_packets =+ tx_packets; - u64_stats_update_end(&stats->tx_syncp); - - return tx_packets; -} - static int xmit_skb(struct send_queue *sq, struct sk_buff *skb) { struct skb_vnet_hdr *hdr; @@ -917,6 +952,7 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb) sg_set_buf(sq->sg, hdr, hdr_len); num_sg = skb_to_sgvec(skb, sq->sg + 1, 0, skb->len) + 1; } + return virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, skb, GFP_ATOMIC); } @@ -925,10 +961,11 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) struct virtnet_info *vi = netdev_priv(dev); int qnum = skb_get_queue_mapping(skb); struct send_queue *sq = &vi->sq[qnum]; - int err; + int err, qsize = virtqueue_get_vring_size(sq->vq); + virtqueue_disable_cb(sq->vq); /* Free up any pending old buffers before queueing new ones. */ - free_old_xmit_skbs(sq); + free_old_xmit_skbs(sq, qsize); /* Try to transmit */ err = xmit_skb(sq, skb); @@ -944,22 +981,20 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) return NETDEV_TX_OK; } - /* Don't wait up for transmitted skbs to be freed. */ - skb_orphan(skb); - nf_reset(skb); - /* Apparently nice girls don't return TX_BUSY; stop the queue * before it gets out of hand. Naturally, this wastes entries. */ if (sq->vq->num_free < 2+MAX_SKB_FRAGS) { netif_stop_subqueue(dev, qnum); if (unlikely(!virtqueue_enable_cb_delayed(sq->vq))) { /* More just got used, free them then recheck. */ - free_old_xmit_skbs(sq); + free_old_xmit_skbs(sq, qsize); if (sq->vq->num_free >= 2+MAX_SKB_FRAGS) { netif_start_subqueue(dev, qnum); 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) @@ -1141,8 +1176,10 @@ static int virtnet_close(struct net_device *dev) /* Make sure refill_work doesn't re-enable napi! */ cancel_delayed_work_sync(&vi->refill); - for (i = 0; i < vi->max_queue_pairs; i++) + for (i = 0; i < vi->max_queue_pairs; i++) { napi_disable(&vi->rq[i].napi); + napi_disable(&vi->sq[i].napi); + } return 0; } @@ -1461,8 +1498,10 @@ static void virtnet_free_queues(struct virtnet_info *vi) { int i; - for (i = 0; i < vi->max_queue_pairs; i++) + for (i = 0; i < vi->max_queue_pairs; i++) { netif_napi_del(&vi->rq[i].napi); + netif_napi_del(&vi->sq[i].napi); + } kfree(vi->rq); kfree(vi->sq); @@ -1616,6 +1655,8 @@ static int virtnet_alloc_queues(struct virtnet_info *vi) netif_napi_add(vi->dev, &vi->rq[i].napi, virtnet_poll, napi_weight); napi_hash_add(&vi->rq[i].napi); + netif_napi_add(vi->dev, &vi->sq[i].napi, virtnet_poll_tx, + napi_weight); sg_init_table(vi->rq[i].sg, ARRAY_SIZE(vi->rq[i].sg)); ewma_init(&vi->rq[i].mrg_avg_pkt_len, 1, RECEIVE_AVG_WEIGHT); @@ -1920,8 +1961,10 @@ static int virtnet_freeze(struct virtio_device *vdev) if (netif_running(vi->dev)) { for (i = 0; i < vi->max_queue_pairs; i++) { napi_disable(&vi->rq[i].napi); + napi_disable(&vi->sq[i].napi); napi_hash_del(&vi->rq[i].napi); netif_napi_del(&vi->rq[i].napi); + netif_napi_del(&vi->sq[i].napi); } } @@ -1946,8 +1989,10 @@ static int virtnet_restore(struct virtio_device *vdev) if (!try_fill_recv(&vi->rq[i], GFP_KERNEL)) schedule_delayed_work(&vi->refill, 0); - for (i = 0; i < vi->max_queue_pairs; i++) + for (i = 0; i < vi->max_queue_pairs; i++) { virtnet_napi_enable(&vi->rq[i]); + napi_enable(&vi->sq[i].napi); + } } netif_device_attach(vi->dev); -- 1.7.1