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Date: Wed, 15 Oct 2014 17:32:06 +0300
From: "Michael S. Tsirkin" <mst@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: Jason Wang <jasowang@...hat.com>,
Rusty Russell <rusty@...tcorp.com.au>,
virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org
Subject: [PATCH RFC v2 2/3] virtio_net: bql
Improve tx batching using byte queue limits.
Should be especially effective for MQ.
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---
drivers/net/virtio_net.c | 20 ++++++++++++++++----
1 file changed, 16 insertions(+), 4 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index a9bf178..8dea411 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -219,13 +219,15 @@ static struct page *get_a_page(struct receive_queue *rq, gfp_t gfp_mask)
return p;
}
-static unsigned int free_old_xmit_skbs(struct send_queue *sq, int budget)
+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;
+ unsigned int bytes = 0;
while (packets < budget &&
(skb = virtqueue_get_buf(sq->vq, &len)) != NULL) {
@@ -233,6 +235,7 @@ static unsigned int free_old_xmit_skbs(struct send_queue *sq, int budget)
u64_stats_update_begin(&stats->tx_syncp);
stats->tx_bytes += skb->len;
+ bytes += skb->len;
stats->tx_packets++;
u64_stats_update_end(&stats->tx_syncp);
@@ -240,6 +243,8 @@ static unsigned int free_old_xmit_skbs(struct send_queue *sq, int budget)
packets++;
}
+ netdev_tx_completed_queue(txq, packets, bytes);
+
return packets;
}
@@ -810,7 +815,7 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget)
again:
__netif_tx_lock(txq, smp_processor_id());
virtqueue_disable_cb(sq->vq);
- sent += free_old_xmit_skbs(sq, budget - sent);
+ sent += free_old_xmit_skbs(txq, sq, budget - sent);
if (sent < budget) {
enable_done = virtqueue_enable_cb_delayed(sq->vq);
@@ -962,12 +967,13 @@ 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;
bool stopped;
+ unsigned int bytes = skb->len;
virtqueue_disable_cb(sq->vq);
/* We are going to push one skb.
* Try to pop one off to free space for it. */
- free_old_xmit_skbs(sq, 1);
+ free_old_xmit_skbs(txq, sq, 1);
/* Try to transmit */
err = xmit_skb(sq, skb);
@@ -983,6 +989,12 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
return NETDEV_TX_OK;
}
+ netdev_tx_sent_queue(txq, bytes);
+
+ /* Kick early so device can process descriptors in parallel with us. */
+ if (kick)
+ virtqueue_kick(sq->vq);
+
/* 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) {
@@ -997,7 +1009,7 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
if (unlikely(!virtqueue_enable_cb_delayed(sq->vq))) {
/* More just got used, free them then recheck. */
- free_old_xmit_skbs(sq, qsize);
+ free_old_xmit_skbs(txq, sq, qsize);
if (stopped && sq->vq->num_free >= 2+MAX_SKB_FRAGS)
netif_start_subqueue(dev, qnum);
}
--
MST
--
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