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Message-Id: <1417429028-11971-2-git-send-email-jasowang@redhat.com>
Date: Mon, 1 Dec 2014 18:17:04 +0800
From: Jason Wang <jasowang@...hat.com>
To: mst@...hat.com, virtualization@...ts.linux-foundation.org,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
davem@...emloft.net
Cc: pagupta@...hat.com, Jason Wang <jasowang@...hat.com>,
Rusty Russell <rusty@...tcorp.com.au>
Subject: [PATCH RFC v4 net-next 1/5] 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.
Note: this might degrade performance for
hosts without event idx support.
Should be addressed by the next patch.
Cc: Rusty Russell <rusty@...tcorp.com.au>
Cc: Michael S. Tsirkin <mst@...hat.com>
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
Signed-off-by: Jason Wang <jasowang@...hat.com>
---
drivers/net/virtio_net.c | 132 +++++++++++++++++++++++++++++++----------------
1 file changed, 88 insertions(+), 44 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index ec2a8b4..f68114e 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 */
@@ -137,6 +139,9 @@ struct virtnet_info {
/* CPU hot plug notifier */
struct notifier_block nb;
+
+ /* Budget for polling tx completion */
+ u32 tx_work_limit;
};
struct skb_vnet_hdr {
@@ -211,15 +216,41 @@ 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)
@@ -777,6 +808,32 @@ 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));
+ u32 limit = vi->tx_work_limit;
+ unsigned int sent;
+
+ __netif_tx_lock(txq, smp_processor_id());
+ sent = free_old_xmit_skbs(txq, sq, limit);
+ if (sent < limit) {
+ 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 < limit ? 0 : budget;
+}
+
#ifdef CONFIG_NET_RX_BUSY_POLL
/* must be called with local_bh_disable()d */
static int virtnet_busy_poll(struct napi_struct *napi)
@@ -825,30 +882,12 @@ 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;
@@ -912,7 +951,9 @@ 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)
@@ -924,8 +965,7 @@ 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);
@@ -941,27 +981,19 @@ 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);
+ if (unlikely(!virtqueue_enable_cb_delayed(sq->vq))) {
+ virtqueue_disable_cb(sq->vq);
+ napi_schedule(&sq->napi);
+ }
+
return NETDEV_TX_OK;
}
@@ -1138,8 +1170,10 @@ 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;
}
@@ -1452,8 +1486,10 @@ 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);
@@ -1607,6 +1643,8 @@ 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);
@@ -1790,6 +1828,8 @@ static int virtnet_probe(struct virtio_device *vdev)
if (err)
goto free_stats;
+ vi->tx_work_limit = napi_weight;
+
#ifdef CONFIG_SYSFS
if (vi->mergeable_rx_bufs)
dev->sysfs_rx_queue_group = &virtio_net_mrg_rx_group;
@@ -1904,8 +1944,10 @@ 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);
}
}
@@ -1930,8 +1972,10 @@ 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);
--
1.8.3.1
--
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