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Commit 11274e5a authored by Stephen Hemminger's avatar Stephen Hemminger Committed by David S. Miller
Browse files

[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: default avatarStephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 075aa573

net/sched/sch_api.c

+3 −0
Original line number Diff line number Diff line
@@ -298,6 +298,7 @@ static enum hrtimer_restart qdisc_watchdog(struct hrtimer *timer) 
						 timer);



	wd->qdisc->flags &= ~TCQ_F_THROTTLED;

	smp_wmb();

	netif_schedule(wd->qdisc->dev);

	return HRTIMER_NORESTART;

}
@@ -315,6 +316,7 @@ void qdisc_watchdog_schedule(struct qdisc_watchdog *wd, psched_time_t expires) 
	ktime_t time;



	wd->qdisc->flags |= TCQ_F_THROTTLED;

	smp_wmb();

	time = ktime_set(0, 0);

	time = ktime_add_ns(time, PSCHED_US2NS(expires));

	hrtimer_start(&wd->timer, time, HRTIMER_MODE_ABS);
@@ -325,6 +327,7 @@ void qdisc_watchdog_cancel(struct qdisc_watchdog *wd) 
{

	hrtimer_cancel(&wd->timer);

	wd->qdisc->flags &= ~TCQ_F_THROTTLED;

	smp_wmb();

}

EXPORT_SYMBOL(qdisc_watchdog_cancel);

net/sched/sch_netem.c

+13 −10
Original line number Diff line number Diff line
@@ -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) {

		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: queue discpline %s could not requeue\n",

			printk(KERN_ERR "netem: %s could not requeue\n",

			       q->qdisc->ops->id);

		}

		}



		qdisc_watchdog_schedule(&q->watchdog, cb->time_to_send);

	}



	return NULL;