[NETEM]: avoid excessive requeues

The netem code would call getnstimeofday() and dequeue/requeue after
every packet, even if it was waiting. Avoid this overhead by using
the throttled flag.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 10 deletions

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 7e9e658d4d93..fb49e9e7ace0 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -273,6 +273,10 @@ static struct sk_buff *netem_dequeue(struct Qdisc *sch)
         struct netem_sched_data *q = qdisc_priv(sch);
         struct sk_buff *skb;
 
+        smp_mb();
+        if (sch->flags & TCQ_F_THROTTLED)
+                return NULL;
+
         skb = q->qdisc->dequeue(q->qdisc);
         if (skb) {
                 const struct netem_skb_cb *cb
@@ -285,18 +289,17 @@ static struct sk_buff *netem_dequeue(struct Qdisc *sch)
                 if (PSCHED_TLESS(cb->time_to_send, now)) {
                         pr_debug("netem_dequeue: return skb=%p\n", skb);
                         sch->q.qlen--;
-                        sch->flags &= ~TCQ_F_THROTTLED;
                         return skb;
-                } else {
-                        qdisc_watchdog_schedule(&q->watchdog, cb->time_to_send);
-
-                        if (q->qdisc->ops->requeue(skb, q->qdisc) != NET_XMIT_SUCCESS) {
-                                qdisc_tree_decrease_qlen(q->qdisc, 1);
-                                sch->qstats.drops++;
-                                printk(KERN_ERR "netem: queue discpline %s could not requeue\n",
-                                       q->qdisc->ops->id);
-                        }
                 }
+
+                if (unlikely(q->qdisc->ops->requeue(skb, q->qdisc) != NET_XMIT_SUCCESS)) {
+                        qdisc_tree_decrease_qlen(q->qdisc, 1);
+                        sch->qstats.drops++;
+                        printk(KERN_ERR "netem: %s could not requeue\n",
+                               q->qdisc->ops->id);
+                }
+
+                qdisc_watchdog_schedule(&q->watchdog, cb->time_to_send);
         }
 
         return NULL;