Merge branch 'remove-qdisc-throttle'

Eric Dumazet says:

====================
net_sched: remove qdisc_is_throttled()

HTB, CBQ and HFSC pay a very high cost updating the qdisc 'throttled'
status that nothing but CBQ seems to use.

CBQ usage is flaky anyway, since no qdisc ->enqueue() updates the
'throttled' qdisc status.

This looks like some 'optimization' that actually cost more than code
without the optimization, and might cause latency issues with CBQ.

In my tests, I could achieve a 8 % performance increase in TCP_RR
workload through HTB qdisc, in presence of throttled classes,
and 5 % without throttled classes.
====================
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/pkt_sched.h

@@ -67,12 +67,12 @@ struct qdisc_watchdog {
 };
 
 void qdisc_watchdog_init(struct qdisc_watchdog *wd, struct Qdisc *qdisc);
-void qdisc_watchdog_schedule_ns(struct qdisc_watchdog *wd, u64 expires, bool throttle);
+void qdisc_watchdog_schedule_ns(struct qdisc_watchdog *wd, u64 expires);
 
 static inline void qdisc_watchdog_schedule(struct qdisc_watchdog *wd,
 					   psched_time_t expires)
 {
-	qdisc_watchdog_schedule_ns(wd, PSCHED_TICKS2NS(expires), true);
+	qdisc_watchdog_schedule_ns(wd, PSCHED_TICKS2NS(expires));
 }
 
 void qdisc_watchdog_cancel(struct qdisc_watchdog *wd);

include/net/sch_generic.h

@@ -26,7 +26,6 @@ struct qdisc_rate_table {
 enum qdisc_state_t {
 	__QDISC_STATE_SCHED,
 	__QDISC_STATE_DEACTIVATED,
-	__QDISC_STATE_THROTTLED,
 };
 
 struct qdisc_size_table {
@@ -125,21 +124,6 @@ static inline int qdisc_avail_bulklimit(const struct netdev_queue *txq)
 #endif
 }
 
-static inline bool qdisc_is_throttled(const struct Qdisc *qdisc)
-{
-	return test_bit(__QDISC_STATE_THROTTLED, &qdisc->state) ? true : false;
-}
-
-static inline void qdisc_throttled(struct Qdisc *qdisc)
-{
-	set_bit(__QDISC_STATE_THROTTLED, &qdisc->state);
-}
-
-static inline void qdisc_unthrottled(struct Qdisc *qdisc)
-{
-	clear_bit(__QDISC_STATE_THROTTLED, &qdisc->state);
-}
-
 struct Qdisc_class_ops {
 	/* Child qdisc manipulation */
 	struct netdev_queue *	(*select_queue)(struct Qdisc *, struct tcmsg *);

net/sched/sch_api.c

@@ -583,7 +583,6 @@ static enum hrtimer_restart qdisc_watchdog(struct hrtimer *timer)
 						 timer);
 
 	rcu_read_lock();
-	qdisc_unthrottled(wd->qdisc);
 	__netif_schedule(qdisc_root(wd->qdisc));
 	rcu_read_unlock();
 
@@ -598,15 +597,12 @@ void qdisc_watchdog_init(struct qdisc_watchdog *wd, struct Qdisc *qdisc)
 }
 EXPORT_SYMBOL(qdisc_watchdog_init);
 
-void qdisc_watchdog_schedule_ns(struct qdisc_watchdog *wd, u64 expires, bool throttle)
+void qdisc_watchdog_schedule_ns(struct qdisc_watchdog *wd, u64 expires)
 {
 	if (test_bit(__QDISC_STATE_DEACTIVATED,
 		     &qdisc_root_sleeping(wd->qdisc)->state))
 		return;
 
-	if (throttle)
-		qdisc_throttled(wd->qdisc);
-
 	if (wd->last_expires == expires)
 		return;
 
@@ -620,7 +616,6 @@ EXPORT_SYMBOL(qdisc_watchdog_schedule_ns);
 void qdisc_watchdog_cancel(struct qdisc_watchdog *wd)
 {
 	hrtimer_cancel(&wd->timer);
-	qdisc_unthrottled(wd->qdisc);
 }
 EXPORT_SYMBOL(qdisc_watchdog_cancel);
 

net/sched/sch_cbq.c

@@ -345,7 +345,7 @@ cbq_mark_toplevel(struct cbq_sched_data *q, struct cbq_class *cl)
 {
 	int toplevel = q->toplevel;
 
-	if (toplevel > cl->level && !(qdisc_is_throttled(cl->q))) {
+	if (toplevel > cl->level) {
 		psched_time_t now = psched_get_time();
 
 		do {
@@ -513,7 +513,6 @@ static enum hrtimer_restart cbq_undelay(struct hrtimer *timer)
 		hrtimer_start(&q->delay_timer, time, HRTIMER_MODE_ABS_PINNED);
 	}
 
-	qdisc_unthrottled(sch);
 	__netif_schedule(qdisc_root(sch));
 	return HRTIMER_NORESTART;
 }
@@ -819,7 +818,6 @@ cbq_dequeue(struct Qdisc *sch)
 		if (skb) {
 			qdisc_bstats_update(sch, skb);
 			sch->q.qlen--;
-			qdisc_unthrottled(sch);
 			return skb;
 		}
 

net/sched/sch_fq.c

@@ -445,8 +445,7 @@ static struct sk_buff *fq_dequeue(struct Qdisc *sch)
 		if (!head->first) {
 			if (q->time_next_delayed_flow != ~0ULL)
 				qdisc_watchdog_schedule_ns(&q->watchdog,
-							   q->time_next_delayed_flow,
-							   false);
+							   q->time_next_delayed_flow);
 			return NULL;
 		}
 	}

net/sched/sch_hfsc.c

@@ -1664,7 +1664,6 @@ hfsc_dequeue(struct Qdisc *sch)
 		set_passive(cl);
 	}
 
-	qdisc_unthrottled(sch);
 	qdisc_bstats_update(sch, skb);
 	qdisc_qstats_backlog_dec(sch, skb);
 	sch->q.qlen--;

net/sched/sch_htb.c

@@ -889,7 +889,6 @@ static struct sk_buff *htb_dequeue(struct Qdisc *sch)
 	if (skb != NULL) {
 ok:
 		qdisc_bstats_update(sch, skb);
-		qdisc_unthrottled(sch);
 		qdisc_qstats_backlog_dec(sch, skb);
 		sch->q.qlen--;
 		return skb;
@@ -929,7 +928,7 @@ static struct sk_buff *htb_dequeue(struct Qdisc *sch)
 	}
 	qdisc_qstats_overlimit(sch);
 	if (likely(next_event > q->now))
-		qdisc_watchdog_schedule_ns(&q->watchdog, next_event, true);
+		qdisc_watchdog_schedule_ns(&q->watchdog, next_event);
 	else
 		schedule_work(&q->work);
 fin:

net/sched/sch_netem.c

@@ -582,15 +582,11 @@ static struct sk_buff *netem_dequeue(struct Qdisc *sch)
 	struct sk_buff *skb;
 	struct rb_node *p;
 
-	if (qdisc_is_throttled(sch))
-		return NULL;
-
 tfifo_dequeue:
 	skb = __skb_dequeue(&sch->q);
 	if (skb) {
 		qdisc_qstats_backlog_dec(sch, skb);
 deliver:
-		qdisc_unthrottled(sch);
 		qdisc_bstats_update(sch, skb);
 		return skb;
 	}

net/sched/sch_plug.c

@@ -64,6 +64,8 @@ struct plug_sched_data {
 	 */
 	bool unplug_indefinite;
 
+	bool throttled;
+
 	/* Queue Limit in bytes */
 	u32 limit;
 
@@ -103,7 +105,7 @@ static struct sk_buff *plug_dequeue(struct Qdisc *sch)
 {
 	struct plug_sched_data *q = qdisc_priv(sch);
 
-	if (qdisc_is_throttled(sch))
+	if (q->throttled)
 		return NULL;
 
 	if (!q->unplug_indefinite) {
@@ -111,7 +113,7 @@ static struct sk_buff *plug_dequeue(struct Qdisc *sch)
 			/* No more packets to dequeue. Block the queue
 			 * and wait for the next release command.
 			 */
-			qdisc_throttled(sch);
+			q->throttled = true;
 			return NULL;
 		}
 		q->pkts_to_release--;
@@ -141,7 +143,7 @@ static int plug_init(struct Qdisc *sch, struct nlattr *opt)
 		q->limit = ctl->limit;
 	}
 
-	qdisc_throttled(sch);
+	q->throttled = true;
 	return 0;
 }
 
@@ -173,7 +175,7 @@ static int plug_change(struct Qdisc *sch, struct nlattr *opt)
 		q->pkts_last_epoch = q->pkts_current_epoch;
 		q->pkts_current_epoch = 0;
 		if (q->unplug_indefinite)
-			qdisc_throttled(sch);
+			q->throttled = true;
 		q->unplug_indefinite = false;
 		break;
 	case TCQ_PLUG_RELEASE_ONE:
@@ -182,7 +184,7 @@ static int plug_change(struct Qdisc *sch, struct nlattr *opt)
 		 */
 		q->pkts_to_release += q->pkts_last_epoch;
 		q->pkts_last_epoch = 0;
-		qdisc_unthrottled(sch);
+		q->throttled = false;
 		netif_schedule_queue(sch->dev_queue);
 		break;
 	case TCQ_PLUG_RELEASE_INDEFINITE:
@@ -190,7 +192,7 @@ static int plug_change(struct Qdisc *sch, struct nlattr *opt)
 		q->pkts_to_release = 0;
 		q->pkts_last_epoch = 0;
 		q->pkts_current_epoch = 0;
-		qdisc_unthrottled(sch);
+		q->throttled = false;
 		netif_schedule_queue(sch->dev_queue);
 		break;
 	case TCQ_PLUG_LIMIT:

net/sched/sch_tbf.c

@@ -254,14 +254,12 @@ static struct sk_buff *tbf_dequeue(struct Qdisc *sch)
 			q->ptokens = ptoks;
 			qdisc_qstats_backlog_dec(sch, skb);
 			sch->q.qlen--;
-			qdisc_unthrottled(sch);
 			qdisc_bstats_update(sch, skb);
 			return skb;
 		}
 
 		qdisc_watchdog_schedule_ns(&q->watchdog,
-					   now + max_t(long, -toks, -ptoks),
-					   true);
+					   now + max_t(long, -toks, -ptoks));
 
 		/* Maybe we have a shorter packet in the queue,
 		   which can be sent now. It sounds cool,