[ofa-general] [PATCH 03/10] dev.c changes.

[Krishna Kumar]

Changes in dev.c to support batching : add dev_add_skb_to_blist,
register_netdev recognizes batch aware drivers, and net_tx_action is
the sole user of batching.

Signed-off-by: Krishna Kumar <krkumar2 at in.ibm.com>
---
 dev.c |   77 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 files changed, 74 insertions(+), 3 deletions(-)

diff -ruNp org/net/core/dev.c new/net/core/dev.c
--- org/net/core/dev.c	2007-07-20 07:49:28.000000000 +0530
+++ new/net/core/dev.c	2007-07-20 08:31:35.000000000 +0530
@@ -1414,6 +1414,45 @@ static int dev_gso_segment(struct sk_buf
 	return 0;
 }
 
+/*
+ * Add skb (skbs in case segmentation is required) to dev->skb_blist. We are
+ * holding QDISC RUNNING bit, so no one else can add to this list. Also, skbs
+ * are dequeued from this list when we call the driver, so the list is safe
+ * from simultaneous deletes too.
+ *
+ * Returns count of successful skb(s) added to skb_blist.
+ */
+int dev_add_skb_to_blist(struct sk_buff *skb, struct net_device *dev)
+{
+	if (!list_empty(&ptype_all))
+		dev_queue_xmit_nit(skb, dev);
+
+	if (netif_needs_gso(dev, skb)) {
+		if (unlikely(dev_gso_segment(skb))) {
+			kfree(skb);
+			return 0;
+		}
+
+		if (skb->next) {
+			int count = 0;
+
+			do {
+				struct sk_buff *nskb = skb->next;
+
+				skb->next = nskb->next;
+				__skb_queue_tail(dev->skb_blist, nskb);
+				count++;
+			} while (skb->next);
+
+			skb->destructor = DEV_GSO_CB(skb)->destructor;
+			kfree_skb(skb);
+			return count;
+		}
+	}
+	__skb_queue_tail(dev->skb_blist, skb);
+	return 1;
+}
+
 int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	if (likely(!skb->next)) {
@@ -1566,7 +1605,7 @@ gso:
 			/* reset queue_mapping to zero */
 			skb->queue_mapping = 0;
 			rc = q->enqueue(skb, q);
-			qdisc_run(dev);
+			qdisc_run(dev, NULL);
 			spin_unlock(&dev->queue_lock);
 
 			rc = rc == NET_XMIT_BYPASS ? NET_XMIT_SUCCESS : rc;
@@ -1763,7 +1802,11 @@ static void net_tx_action(struct softirq
 			clear_bit(__LINK_STATE_SCHED, &dev->state);
 
 			if (spin_trylock(&dev->queue_lock)) {
-				qdisc_run(dev);
+				/*
+				 * Try to send out all skbs if batching is
+				 * enabled.
+				 */
+				qdisc_run(dev, dev->skb_blist);
 				spin_unlock(&dev->queue_lock);
 			} else {
 				netif_schedule(dev);
@@ -3397,6 +3440,28 @@ int register_netdevice(struct net_device
 		}
 	}
 
+	if (dev->features & NETIF_F_BATCH_SKBS) {
+		if (!dev->hard_start_xmit_batch ||
+		    dev->tx_queue_len < MIN_QUEUE_LEN_BATCH) {
+			/*
+			 * Batch TX requires API support in driver plus have
+			 * a minimum sized queue.
+			 */
+			printk(KERN_ERR "%s: Dropping NETIF_F_BATCH_SKBS "
+					"since no API support or queue len "
+					"is smaller than %d.\n",
+					dev->name, MIN_QUEUE_LEN_BATCH);
+			dev->features &= ~NETIF_F_BATCH_SKBS;
+		} else {
+			dev->skb_blist = kmalloc(sizeof *dev->skb_blist,
+						 GFP_KERNEL);
+			if (dev->skb_blist) {
+				skb_queue_head_init(dev->skb_blist);
+				dev->tx_queue_len >>= 1;
+			}
+		}
+	}
+
 	/*
 	 *	nil rebuild_header routine,
 	 *	that should be never called and used as just bug trap.
@@ -3732,10 +3797,16 @@ void unregister_netdevice(struct net_dev
 
 	synchronize_net();
 
+	/* Deallocate batching structure */
+	if (dev->skb_blist) {
+		skb_queue_purge(dev->skb_blist);
+		kfree(dev->skb_blist);
+		dev->skb_blist = NULL;
+	}
+
 	/* Shutdown queueing discipline. */
 	dev_shutdown(dev);
 
-
 	/* Notify protocols, that we are about to destroy
 	   this device. They should clean all the things.
 	*/