[ofa-general] [PATCH 05/10] sch_generic.c changes.
Krishna Kumar
krkumar2 at in.ibm.com
Thu Jul 19 23:32:49 PDT 2007
net/sched/sch_generic.c changes to support batching. Adds a batch
aware function (get_skb) to get skbs to send.
Signed-off-by: Krishna Kumar <krkumar2 at in.ibm.com>
---
sch_generic.c | 94 +++++++++++++++++++++++++++++++++++++++++++---------------
1 files changed, 71 insertions(+), 23 deletions(-)
diff -ruNp org/net/sched/sch_generic.c new/net/sched/sch_generic.c
--- org/net/sched/sch_generic.c 2007-07-20 07:49:28.000000000 +0530
+++ new/net/sched/sch_generic.c 2007-07-20 08:30:22.000000000 +0530
@@ -9,6 +9,11 @@
* Authors: Alexey Kuznetsov, <kuznet at ms2.inr.ac.ru>
* Jamal Hadi Salim, <hadi at cyberus.ca> 990601
* - Ingress support
+ *
+ * New functionality:
+ * Krishna Kumar, <krkumar2 at in.ibm.com>, July 2007
+ * - Support for sending multiple skbs to devices that support
+ * new api - dev->hard_start_xmit_batch()
*/
#include <linux/bitops.h>
@@ -59,10 +64,12 @@ static inline int qdisc_qlen(struct Qdis
static inline int dev_requeue_skb(struct sk_buff *skb, struct net_device *dev,
struct Qdisc *q)
{
- if (unlikely(skb->next))
- dev->gso_skb = skb;
- else
- q->ops->requeue(skb, q);
+ if (likely(skb)) {
+ if (unlikely(skb->next))
+ dev->gso_skb = skb;
+ else
+ q->ops->requeue(skb, q);
+ }
netif_schedule(dev);
return 0;
@@ -91,18 +98,23 @@ static inline int handle_dev_cpu_collisi
/*
* Same CPU holding the lock. It may be a transient
* configuration error, when hard_start_xmit() recurses. We
- * detect it by checking xmit owner and drop the packet when
- * deadloop is detected. Return OK to try the next skb.
+ * detect it by checking xmit owner and drop skb (or all
+ * skbs in batching case) when deadloop is detected. Return
+ * OK to try the next skb.
*/
- kfree_skb(skb);
+ if (likely(skb))
+ kfree_skb(skb);
+ else if (!skb_queue_empty(dev->skb_blist))
+ skb_queue_purge(dev->skb_blist);
+
if (net_ratelimit())
printk(KERN_WARNING "Dead loop on netdevice %s, "
"fix it urgently!\n", dev->name);
ret = qdisc_qlen(q);
} else {
/*
- * Another cpu is holding lock, requeue & delay xmits for
- * some time.
+ * Another cpu is holding lock. Requeue skb and delay xmits
+ * for some time.
*/
__get_cpu_var(netdev_rx_stat).cpu_collision++;
ret = dev_requeue_skb(skb, dev, q);
@@ -112,6 +124,39 @@ static inline int handle_dev_cpu_collisi
}
/*
+ * Algorithm to get skb(s) is:
+ * - Non batching drivers, or if the batch list is empty and there is 1
+ * skb in the queue - dequeue skb and put it in *skbp to tell the
+ * caller to use the regular API.
+ * - Batching drivers where the batch list already contains atleast one
+ * skb or if there are multiple skbs in the queue: keep dequeue'ing
+ * skb's upto a limit and set *skbp to NULL to tell the caller to use
+ * the new API.
+ *
+ * Returns:
+ * 1 - atleast one skb is to be sent out, *skbp contains skb or NULL
+ * (in case >1 skbs present in blist for batching)
+ * 0 - no skbs to be sent.
+ */
+static inline int get_skb(struct net_device *dev, struct Qdisc *q,
+ struct sk_buff_head *blist,
+ struct sk_buff **skbp)
+{
+ if (likely(!blist) || (!skb_queue_len(blist) && qdisc_qlen(q) <= 1)) {
+ return likely((*skbp = dev_dequeue_skb(dev, q)) != NULL);
+ } else {
+ int max = dev->tx_queue_len - skb_queue_len(blist);
+ struct sk_buff *skb;
+
+ while (max > 0 && (skb = dev_dequeue_skb(dev, q)) != NULL)
+ max -= dev_add_skb_to_blist(skb, dev);
+
+ *skbp = NULL;
+ return 1; /* we have atleast one skb in blist */
+ }
+}
+
+/*
* NOTE: Called under dev->queue_lock with locally disabled BH.
*
* __LINK_STATE_QDISC_RUNNING guarantees only one CPU can process this
@@ -130,27 +175,28 @@ static inline int handle_dev_cpu_collisi
* >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 *blist)
{
struct Qdisc *q = dev->qdisc;
struct sk_buff *skb;
- unsigned lockless;
+ unsigned getlock; /* whether we need to get lock or not */
int ret;
/* Dequeue packet */
- if (unlikely((skb = dev_dequeue_skb(dev, q)) == NULL))
+ if (unlikely(!get_skb(dev, q, blist, &skb)))
return 0;
/*
* When the driver has LLTX set, it does its own locking in
- * start_xmit. These checks are worth it because even uncongested
+ * start_xmit. These checks are worth it because even uncontested
* locks can be quite expensive. The driver can do a trylock, as
* is being done here; in case of lock contention it should return
* NETDEV_TX_LOCKED and the packet will be requeued.
*/
- lockless = (dev->features & NETIF_F_LLTX);
+ getlock = !(dev->features & NETIF_F_LLTX);
- if (!lockless && !netif_tx_trylock(dev)) {
+ if (getlock && !netif_tx_trylock(dev)) {
/* Another CPU grabbed the driver tx lock */
return handle_dev_cpu_collision(skb, dev, q);
}
@@ -158,9 +204,12 @@ static inline int qdisc_restart(struct n
/* And release queue */
spin_unlock(&dev->queue_lock);
- ret = dev_hard_start_xmit(skb, dev);
+ if (likely(skb))
+ ret = dev_hard_start_xmit(skb, dev);
+ else
+ ret = dev->hard_start_xmit_batch(dev);
- if (!lockless)
+ if (getlock)
netif_tx_unlock(dev);
spin_lock(&dev->queue_lock);
@@ -168,7 +217,7 @@ static inline int qdisc_restart(struct n
switch (ret) {
case NETDEV_TX_OK:
- /* Driver sent out skb successfully */
+ /* Driver sent out skb (or entire skb_blist) successfully */
ret = qdisc_qlen(q);
break;
@@ -179,10 +228,9 @@ static inline int qdisc_restart(struct n
default:
/* Driver returned NETDEV_TX_BUSY - requeue skb */
- if (unlikely (ret != NETDEV_TX_BUSY && net_ratelimit()))
- printk(KERN_WARNING "BUG %s code %d qlen %d\n",
+ if (unlikely(ret != NETDEV_TX_BUSY) && net_ratelimit())
+ printk(KERN_WARNING " %s: BUG. code %d qlen %d\n",
dev->name, ret, q->q.qlen);
-
ret = dev_requeue_skb(skb, dev, q);
break;
}
@@ -190,10 +238,10 @@ static inline int qdisc_restart(struct n
return ret;
}
-void __qdisc_run(struct net_device *dev)
+void __qdisc_run(struct net_device *dev, struct sk_buff_head *blist)
{
do {
- if (!qdisc_restart(dev))
+ if (!qdisc_restart(dev, blist))
break;
} while (!netif_queue_stopped(dev));
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