[RFC] [PATCH 2/5] net: Use sk_tx_queue_mapping for connected sockets

[Krishna Kumar <krkumar2@in.ibm.com>]

From: Krishna Kumar <krkumar2@in.ibm.com>

For connected sockets, the first run of dev_pick_tx saves the
calculated txq in sk_tx_queue_mapping. This is not saved if
either skb rx was recorded, or if the device has a queue select
handler. Next iterations of dev_pick_tx uses the cached value of
sk_tx_queue_mapping.

Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com>
---
 net/core/dev.c |   24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff -ruNp org/net/core/dev.c new/net/core/dev.c
--- org/net/core/dev.c	2009-10-14 17:59:40.000000000 +0530
+++ new/net/core/dev.c	2009-10-14 18:00:04.000000000 +0530
@@ -1791,13 +1791,25 @@ EXPORT_SYMBOL(skb_tx_hash);
 static struct netdev_queue *dev_pick_tx(struct net_device *dev,
 					struct sk_buff *skb)
 {
-	const struct net_device_ops *ops = dev->netdev_ops;
-	u16 queue_index = 0;
+	u16 queue_index;
+	struct sock *sk = skb->sk;
+
+	if (sk_tx_queue_recorded(sk)) {
+		queue_index = sk_get_tx_queue(sk);
+	} else {
+		const struct net_device_ops *ops = dev->netdev_ops;
 
-	if (ops->ndo_select_queue)
-		queue_index = ops->ndo_select_queue(dev, skb);
-	else if (dev->real_num_tx_queues > 1)
-		queue_index = skb_tx_hash(dev, skb);
+		if (ops->ndo_select_queue) {
+			queue_index = ops->ndo_select_queue(dev, skb);
+		} else {
+			queue_index = 0;
+			if (dev->real_num_tx_queues > 1)
+				queue_index = skb_tx_hash(dev, skb);
+
+			if (sk && sk->sk_dst_cache)
+				sk_record_tx_queue(sk, queue_index);
+		}
+	}
 
 	skb_set_queue_mapping(skb, queue_index);
 	return netdev_get_tx_queue(dev, queue_index);