Commit e69f73bf authored by David S. Miller's avatar David S. Miller
Browse files

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: default avatarDavid S. Miller <davem@davemloft.net>
parents 7a04c012 45f50bed

include/net/pkt_sched.h

+2 −2
Original line number Diff line number Diff line
@@ -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

+0 −16
Original line number Diff line number Diff line
@@ -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

+1 −6
Original line number Diff line number Diff line
@@ -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

+1 −3
Original line number Diff line number Diff line
@@ -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

+1 −2
Original line number Diff line number Diff line
@@ -445,8 +445,7 @@ begin: 
		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;

		}

	}

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