Michael S. Tsirkin
2014-Oct-20 06:52 UTC
[PATCH RFC v3 1/3] virtio_net: enable tx interrupt
On newer hosts that support delayed tx interrupts, we probably don't have much to gain from orphaning packets early. Based on patch by Jason Wang. Note: this might degrade performance for hosts without event idx support. Should be addressed by the next patch. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- drivers/net/virtio_net.c | 133 +++++++++++++++++++++++++++++++---------------- 1 file changed, 89 insertions(+), 44 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 13d0a8b..14f4cda 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 +219,41 @@ static struct page *get_a_page(struct receive_queue *rq, gfp_t gfp_mask) return p; } +static unsigned int free_old_xmit_skbs(struct netdev_queue *txq, + 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); + unsigned int packets = 0; + + while (packets < budget && + (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); + + dev_kfree_skb_any(skb); + packets++; + } + + if (sq->vq->num_free >= 2+MAX_SKB_FRAGS) + netif_tx_start_queue(txq); + + return 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)); + virtqueue_disable_cb(sq->vq); + napi_schedule(&sq->napi); } static unsigned int mergeable_ctx_to_buf_truesize(unsigned long mrg_ctx) @@ -774,6 +802,31 @@ 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 sent; + + __netif_tx_lock(txq, smp_processor_id()); + sent = free_old_xmit_skbs(txq, sq, budget); + if (sent < budget) { + napi_complete(napi); + /* Note: we must enable cb *after* napi_complete, because + * napi_schedule calls from callbacks that trigger before + * napi_complete are ignored. + */ + if (unlikely(!virtqueue_enable_cb_delayed(sq->vq))) { + virtqueue_disable_cb(sq->vq); + napi_schedule(&sq->napi); + } + } + __netif_tx_unlock(txq); + 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) @@ -822,30 +875,12 @@ 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 void 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); - - 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); - - dev_kfree_skb_any(skb); - } -} - static int xmit_skb(struct send_queue *sq, struct sk_buff *skb) { struct skb_vnet_hdr *hdr; @@ -911,7 +946,9 @@ 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); + + return virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, skb, + GFP_ATOMIC); } static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) @@ -923,8 +960,7 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) struct netdev_queue *txq = netdev_get_tx_queue(dev, qnum); bool kick = !skb->xmit_more; - /* Free up any pending old buffers before queueing new ones. */ - free_old_xmit_skbs(sq); + virtqueue_disable_cb(sq->vq); /* Try to transmit */ err = xmit_skb(sq, skb); @@ -940,27 +976,26 @@ 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) { + 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); - if (sq->vq->num_free >= 2+MAX_SKB_FRAGS) { - netif_start_subqueue(dev, qnum); - virtqueue_disable_cb(sq->vq); - } - } - } if (kick || netif_xmit_stopped(txq)) virtqueue_kick(sq->vq); + /* Try to pop off some buffers before we re-enable callbacks. + * It makes sense to do it after kick, since that causes + * device to process packets. + */ + if (free_old_xmit_skbs(txq, sq, NAPI_POLL_WEIGHT) < NAPI_POLL_WEIGHT) { + if (unlikely(!virtqueue_enable_cb_delayed(sq->vq))) { + virtqueue_disable_cb(sq->vq); + napi_schedule(&sq->napi); + } + } else { + napi_schedule(&sq->napi); + } return NETDEV_TX_OK; } @@ -1137,8 +1172,10 @@ 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; } @@ -1457,8 +1494,10 @@ 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); @@ -1612,6 +1651,8 @@ 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); @@ -1916,8 +1957,10 @@ 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); } } @@ -1942,8 +1985,10 @@ 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); -- MST
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