Subject: [ofa-general] [PATCH 2/3][NET_BATCH] net core use batching

From: jamal <[email-masked]>
Date: Sun, 07 Oct 2007 14:38:09 -0400

This patch adds the usage of batching within the core.

cheers,
jamal

[NET_BATCH] net core use batching

This patch adds the usage of batching within the core.
Performance results demonstrating improvement are provided separately.

I have #if-0ed some of the old functions so the patch is more readable.
A future patch will remove all if-0ed content.
Patrick McHardy eyeballed a bug that will cause re-ordering in case
of a requeue.

Signed-off-by: Jamal Hadi Salim <[email-masked]>

---
commit cd602aa5f84fcef6359852cd99c95863eeb91015
tree f31d2dde4f138ff6789682163624bc0f8541aa77
parent 0a0762e2c615a980af284e86d9729d233e1bf7f4
author Jamal Hadi Salim <[email-masked]> Sun, 07 Oct 2007 09:13:04 -0400
committer Jamal Hadi Salim <[email-masked]> Sun, 07 Oct 2007 09:13:04 -0400

 net/sched/sch_generic.c |  132 +++++++++++++++++++++++++++++++++++++++++++----
 1 files changed, 120 insertions(+), 12 deletions(-)

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 95ae119..80ac56b 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -56,6 +56,7 @@ static inline int qdisc_qlen(struct Qdisc *q)
 	return q->q.qlen;
 }
 
+#if 0
 static inline int dev_requeue_skb(struct sk_buff *skb, struct net_device *dev,
 				  struct Qdisc *q)
 {
@@ -110,6 +111,97 @@ static inline int handle_dev_cpu_collision(struct sk_buff *skb,
 
 	return ret;
 }
+#endif
+
+static inline int handle_dev_cpu_collision(struct net_device *dev)
+{
+	if (unlikely(dev->xmit_lock_owner == smp_processor_id())) {
+		if (net_ratelimit())
+			printk(KERN_WARNING
+				"Dead loop on netdevice %s, fix it urgently!\n",
+				dev->name);
+		return 1;
+	}
+	__get_cpu_var(netdev_rx_stat).cpu_collision++;
+	return 0;
+}
+
+static inline int
+dev_requeue_skbs(struct sk_buff_head *skbs, struct net_device *dev,
+	       struct Qdisc *q)
+{
+
+	struct sk_buff *skb;
+
+	while ((skb = __skb_dequeue_tail(skbs)) != NULL)
+		q->ops->requeue(skb, q);
+
+	netif_schedule(dev);
+	return 0;
+}
+
+static inline int
+xmit_islocked(struct sk_buff_head *skbs, struct net_device *dev,
+	    struct Qdisc *q)
+{
+	int ret = handle_dev_cpu_collision(dev);
+
+	if (ret) {
+		if (!skb_queue_empty(skbs))
+			skb_queue_purge(skbs);
+		return qdisc_qlen(q);
+	}
+
+	return dev_requeue_skbs(skbs, dev, q);
+}
+
+static int xmit_count_skbs(struct sk_buff *skb)
+{
+	int count = 0;
+	for (; skb; skb = skb->next) {
+		count += skb_shinfo(skb)->nr_frags;
+		count += 1;
+	}
+	return count;
+}
+
+static int xmit_get_pkts(struct net_device *dev,
+			   struct Qdisc *q,
+			   struct sk_buff_head *pktlist)
+{
+	struct sk_buff *skb;
+	int count = dev->xmit_win;
+
+	if (count  && dev->gso_skb) {
+		skb = dev->gso_skb;
+		dev->gso_skb = NULL;
+		count -= xmit_count_skbs(skb);
+		__skb_queue_tail(pktlist, skb);
+	}
+
+	while (count > 0) {
+		skb = q->dequeue(q);
+		if (!skb)
+			break;
+
+		count -= xmit_count_skbs(skb);
+		__skb_queue_tail(pktlist, skb);
+	}
+
+	return skb_queue_len(pktlist);
+}
+
+static int xmit_prepare_pkts(struct net_device *dev,
+			     struct sk_buff_head *tlist)
+{
+	struct sk_buff *skb;
+	struct sk_buff_head *flist = &dev->blist;
+
+	while ((skb = __skb_dequeue(tlist)) != NULL)
+		xmit_prepare_skb(skb, dev);
+
+	return skb_queue_len(flist);
+}
 
 /*
  * NOTE: Called under dev->queue_lock with locally disabled BH.
@@ -130,22 +222,32 @@ static inline int handle_dev_cpu_collision(struct sk_buff *skb,
  *				>0 - queue is not empty.
  *
  */
-static inline int qdisc_restart(struct net_device *dev)
+
+static inline int qdisc_restart(struct net_device *dev,
+				struct sk_buff_head *tpktlist)
 {
 	struct Qdisc *q = dev->qdisc;
-	struct sk_buff *skb;
-	int ret;
+	int ret = 0;
 
-	/* Dequeue packet */
-	if (unlikely((skb = dev_dequeue_skb(dev, q)) == NULL))
-		return 0;
+	/* use of tpktlist reduces the amount of time we sit
+	 * holding the queue_lock
+	*/
+	ret = xmit_get_pkts(dev, q, tpktlist);
 
+	if (!ret)
+		return 0;
 
-	/* And release queue */
+	/* We got em packets */
 	spin_unlock(&dev->queue_lock);
 
+	/* prepare to embark, no locks held moves packets
+	* to dev->blist
+	* */
+	xmit_prepare_pkts(dev, tpktlist);
+
+	/* bye packets ....*/
 	HARD_TX_LOCK(dev, smp_processor_id());
-	ret = dev_hard_start_xmit(skb, dev);
+	ret = dev_batch_xmit(dev);
 	HARD_TX_UNLOCK(dev);
 
 	spin_lock(&dev->queue_lock);
@@ -158,8 +260,8 @@ static inline int qdisc_restart(struct net_device *dev)
 		break;
 
 	case NETDEV_TX_LOCKED:
-		/* Driver try lock failed */
-		ret = handle_dev_cpu_collision(skb, dev, q);
+		/* Driver lock failed */
+		ret = xmit_islocked(&dev->blist, dev, q);
 		break;
 
 	default:
@@ -168,7 +270,7 @@ static inline int qdisc_restart(struct net_device *dev)
 			printk(KERN_WARNING "BUG %s code %d qlen %d\n",
 			       dev->name, ret, q->q.qlen);
 
-		ret = dev_requeue_skb(skb, dev, q);
+		ret = dev_requeue_skbs(&dev->blist, dev, q);
 		break;
 	}
 
@@ -177,8 +279,11 @@ static inline int qdisc_restart(struct net_device *dev)
 
 void __qdisc_run(struct net_device *dev)
 {
+	struct sk_buff_head tpktlist;
+	skb_queue_head_init(&tpktlist);
+
 	do {
-		if (!qdisc_restart(dev))
+		if (!qdisc_restart(dev, &tpktlist))
 			break;
 	} while (!netif_queue_stopped(dev));
 
@@ -564,6 +669,9 @@ void dev_deactivate(struct net_device *dev)
 
 	skb = dev->gso_skb;
 	dev->gso_skb = NULL;
+	if (!skb_queue_empty(&dev->blist))
+		skb_queue_purge(&dev->blist);
+	dev->xmit_win = 1;
 	spin_unlock_bh(&dev->queue_lock);
 
 	kfree_skb(skb);