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Commit d3b6f9ff authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'cbq-fixes' 

Vasily Averin says:

====================
cbq: incorrectly low bandwidth blocks limited traffic

v2: patch description changes
Fixes: f0f6ee1f ("cbq: incorrect processing of high limits")

Mainstream commit f0f6ee1f ("cbq: incorrect processing of high limits")
have side effect: if cbq bandwidth setting is less than real interface
throughput non-limited traffic can delay limited traffic for a very long time.

This happen because of q->now changes incorrectly in cbq_dequeue():
in described scenario L2T is much greater than real time delay,
and q->now gets an extra boost for each transmitted packet.

Accumulated boost prevents update q->now, and blocked class can wait
very long time until (q->now >= cl->undertime) will be true again.

More detailed problem description can be found here:
http://www.spinics.net/lists/netdev/msg292493.html



Following patches should fix the problem.
====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents ac32c7f7 7201c1dd

net/sched/sch_cbq.c

+14 −34
Original line number Original line Diff line number Diff line
@@ -159,7 +159,6 @@ struct cbq_sched_data { 
	struct cbq_class	*tx_borrowed;

	struct cbq_class	*tx_borrowed;

	int			tx_len;

	int			tx_len;

	psched_time_t		now;		/* Cached timestamp */

	psched_time_t		now;		/* Cached timestamp */

	psched_time_t		now_rt;		/* Cached real time */

	unsigned int		pmask;

	unsigned int		pmask;





	struct hrtimer		delay_timer;

	struct hrtimer		delay_timer;
@@ -353,12 +352,7 @@ cbq_mark_toplevel(struct cbq_sched_data *q, struct cbq_class *cl) 
	int toplevel = q->toplevel;

	int toplevel = q->toplevel;





	if (toplevel > cl->level && !(qdisc_is_throttled(cl->q))) {

	if (toplevel > cl->level && !(qdisc_is_throttled(cl->q))) {

		psched_time_t now;

		psched_time_t now = psched_get_time();

		psched_tdiff_t incr;



		now = psched_get_time();

		incr = now - q->now_rt;

		now = q->now + incr;





		do {

		do {

			if (cl->undertime < now) {

			if (cl->undertime < now) {
@@ -700,8 +694,13 @@ cbq_update(struct cbq_sched_data *q) 
	struct cbq_class *this = q->tx_class;

	struct cbq_class *this = q->tx_class;

	struct cbq_class *cl = this;

	struct cbq_class *cl = this;

	int len = q->tx_len;

	int len = q->tx_len;

	psched_time_t now;





	q->tx_class = NULL;

	q->tx_class = NULL;

	/* Time integrator. We calculate EOS time

	 * by adding expected packet transmission time.

	 */

	now = q->now + L2T(&q->link, len);





	for ( ; cl; cl = cl->share) {

	for ( ; cl; cl = cl->share) {

		long avgidle = cl->avgidle;

		long avgidle = cl->avgidle;
@@ -717,7 +716,7 @@ cbq_update(struct cbq_sched_data *q) 
		 *	idle = (now - last) - last_pktlen/rate

		 *	idle = (now - last) - last_pktlen/rate

		 */

		 */





		idle = q->now - cl->last;

		idle = now - cl->last;

		if ((unsigned long)idle > 128*1024*1024) {

		if ((unsigned long)idle > 128*1024*1024) {

			avgidle = cl->maxidle;

			avgidle = cl->maxidle;

		} else {

		} else {
@@ -761,7 +760,7 @@ cbq_update(struct cbq_sched_data *q) 
			idle -= L2T(&q->link, len);

			idle -= L2T(&q->link, len);

			idle += L2T(cl, len);

			idle += L2T(cl, len);





			cl->undertime = q->now + idle;

			cl->undertime = now + idle;

		} else {

		} else {

			/* Underlimit */

			/* Underlimit */
@@ -771,7 +770,8 @@ cbq_update(struct cbq_sched_data *q) 
			else

			else

				cl->avgidle = avgidle;

				cl->avgidle = avgidle;

		}

		}

		cl->last = q->now;

		if ((s64)(now - cl->last) > 0)

			cl->last = now;

	}

	}





	cbq_update_toplevel(q, this, q->tx_borrowed);

	cbq_update_toplevel(q, this, q->tx_borrowed);
@@ -943,31 +943,13 @@ cbq_dequeue(struct Qdisc *sch) 
	struct sk_buff *skb;

	struct sk_buff *skb;

	struct cbq_sched_data *q = qdisc_priv(sch);

	struct cbq_sched_data *q = qdisc_priv(sch);

	psched_time_t now;

	psched_time_t now;

	psched_tdiff_t incr;





	now = psched_get_time();

	now = psched_get_time();

	incr = now - q->now_rt;





	if (q->tx_class) {

	if (q->tx_class)

		psched_tdiff_t incr2;

		/* Time integrator. We calculate EOS time

		 * by adding expected packet transmission time.

		 * If real time is greater, we warp artificial clock,

		 * so that:

		 *

		 * cbq_time = max(real_time, work);

		 */

		incr2 = L2T(&q->link, q->tx_len);

		q->now += incr2;

		cbq_update(q);

		cbq_update(q);

		if ((incr -= incr2) < 0)



			incr = 0;

		q->now += incr;

	} else {

		if (now > q->now)

	q->now = now;

	q->now = now;

	}

	q->now_rt = now;





	for (;;) {

	for (;;) {

		q->wd_expires = 0;

		q->wd_expires = 0;
@@ -1223,7 +1205,6 @@ cbq_reset(struct Qdisc *sch) 
	hrtimer_cancel(&q->delay_timer);

	hrtimer_cancel(&q->delay_timer);

	q->toplevel = TC_CBQ_MAXLEVEL;

	q->toplevel = TC_CBQ_MAXLEVEL;

	q->now = psched_get_time();

	q->now = psched_get_time();

	q->now_rt = q->now;





	for (prio = 0; prio <= TC_CBQ_MAXPRIO; prio++)

	for (prio = 0; prio <= TC_CBQ_MAXPRIO; prio++)

		q->active[prio] = NULL;

		q->active[prio] = NULL;
@@ -1407,7 +1388,6 @@ static int cbq_init(struct Qdisc *sch, struct nlattr *opt) 
	q->delay_timer.function = cbq_undelay;

	q->delay_timer.function = cbq_undelay;

	q->toplevel = TC_CBQ_MAXLEVEL;

	q->toplevel = TC_CBQ_MAXLEVEL;

	q->now = psched_get_time();

	q->now = psched_get_time();

	q->now_rt = q->now;





	cbq_link_class(&q->link);

	cbq_link_class(&q->link);