[PATCH RFC v4 net-next 2/5] virtio_net: bql

From: Jason Wang
Date: Mon Dec 01 2014 - 05:19:10 EST


From: "Michael S. Tsirkin" <mst@xxxxxxxxxx>

Improve tx batching using byte queue limits.
Should be especially effective for MQ.

Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
drivers/net/virtio_net.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index f68114e..0ed24ff 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -224,6 +224,7 @@ static unsigned int free_old_xmit_skbs(struct netdev_queue *txq,
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) {
@@ -231,6 +232,7 @@ static unsigned int free_old_xmit_skbs(struct netdev_queue *txq,

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);

@@ -238,6 +240,8 @@ static unsigned int free_old_xmit_skbs(struct netdev_queue *txq,
packets++;
}

+ netdev_tx_completed_queue(txq, packets, bytes);
+
if (sq->vq->num_free >= 2+MAX_SKB_FRAGS)
netif_tx_start_queue(txq);

@@ -964,6 +968,7 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
int err;
struct netdev_queue *txq = netdev_get_tx_queue(dev, qnum);
bool kick = !skb->xmit_more;
+ unsigned int bytes = skb->len;

virtqueue_disable_cb(sq->vq);

@@ -981,6 +986,8 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
return NETDEV_TX_OK;
}

+ netdev_tx_sent_queue(txq, bytes);
+
/* 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)
--
1.8.3.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/