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Commit 865ec552 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

fq_codel: should use qdisc backlog as threshold 



codel_should_drop() logic allows a packet being not dropped if queue
size is under max packet size.

In fq_codel, we have two possible backlogs : The qdisc global one, and
the flow local one.

The meaningful one for codel_should_drop() should be the global backlog,
not the per flow one, so that thin flows can have a non zero drop/mark
probability.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Dave Taht <dave.taht@bufferbloat.net>
Cc: Kathleen Nichols <nichols@pollere.com>
Cc: Van Jacobson <van@pollere.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c27b46e7

include/net/codel.h

+7 −8
Original line number Diff line number Diff line
@@ -205,7 +205,7 @@ static codel_time_t codel_control_law(codel_time_t t, 




static bool codel_should_drop(const struct sk_buff *skb,

			      unsigned int *backlog,

			      struct Qdisc *sch,

			      struct codel_vars *vars,

			      struct codel_params *params,

			      struct codel_stats *stats,
@@ -219,13 +219,13 @@ static bool codel_should_drop(const struct sk_buff *skb, 
	}



	vars->ldelay = now - codel_get_enqueue_time(skb);

	*backlog -= qdisc_pkt_len(skb);

	sch->qstats.backlog -= qdisc_pkt_len(skb);



	if (unlikely(qdisc_pkt_len(skb) > stats->maxpacket))

		stats->maxpacket = qdisc_pkt_len(skb);



	if (codel_time_before(vars->ldelay, params->target) ||

	    *backlog <= stats->maxpacket) {

	    sch->qstats.backlog <= stats->maxpacket) {

		/* went below - stay below for at least interval */

		vars->first_above_time = 0;

		return false;
@@ -249,8 +249,7 @@ static struct sk_buff *codel_dequeue(struct Qdisc *sch, 
				     struct codel_params *params,

				     struct codel_vars *vars,

				     struct codel_stats *stats,

				     codel_skb_dequeue_t dequeue_func,

				     u32 *backlog)

				     codel_skb_dequeue_t dequeue_func)

{

	struct sk_buff *skb = dequeue_func(vars, sch);

	codel_time_t now;
@@ -261,7 +260,7 @@ static struct sk_buff *codel_dequeue(struct Qdisc *sch, 
		return skb;

	}

	now = codel_get_time();

	drop = codel_should_drop(skb, backlog, vars, params, stats, now);

	drop = codel_should_drop(skb, sch, vars, params, stats, now);

	if (vars->dropping) {

		if (!drop) {

			/* sojourn time below target - leave dropping state */
@@ -292,7 +291,7 @@ static struct sk_buff *codel_dequeue(struct Qdisc *sch, 
				qdisc_drop(skb, sch);

				stats->drop_count++;

				skb = dequeue_func(vars, sch);

				if (!codel_should_drop(skb, backlog,

				if (!codel_should_drop(skb, sch,

						       vars, params, stats, now)) {

					/* leave dropping state */

					vars->dropping = false;
@@ -313,7 +312,7 @@ static struct sk_buff *codel_dequeue(struct Qdisc *sch, 
			stats->drop_count++;



			skb = dequeue_func(vars, sch);

			drop = codel_should_drop(skb, backlog, vars, params,

			drop = codel_should_drop(skb, sch, vars, params,

						 stats, now);

		}

		vars->dropping = true;

net/sched/sch_codel.c

+2 −2
Original line number Diff line number Diff line
@@ -77,8 +77,8 @@ static struct sk_buff *codel_qdisc_dequeue(struct Qdisc *sch) 
	struct codel_sched_data *q = qdisc_priv(sch);

	struct sk_buff *skb;



	skb = codel_dequeue(sch, &q->params, &q->vars, &q->stats,

			    dequeue, &sch->qstats.backlog);

	skb = codel_dequeue(sch, &q->params, &q->vars, &q->stats, dequeue);



	/* We cant call qdisc_tree_decrease_qlen() if our qlen is 0,

	 * or HTB crashes. Defer it for next round.

	 */

net/sched/sch_fq_codel.c

+3 −2
Original line number Diff line number Diff line
@@ -217,13 +217,14 @@ static int fq_codel_enqueue(struct sk_buff *skb, struct Qdisc *sch) 
 */

static struct sk_buff *dequeue(struct codel_vars *vars, struct Qdisc *sch)

{

	struct fq_codel_sched_data *q = qdisc_priv(sch);

	struct fq_codel_flow *flow;

	struct sk_buff *skb = NULL;



	flow = container_of(vars, struct fq_codel_flow, cvars);

	if (flow->head) {

		skb = dequeue_head(flow);

		sch->qstats.backlog -= qdisc_pkt_len(skb);

		q->backlogs[flow - q->flows] -= qdisc_pkt_len(skb);

		sch->q.qlen--;

	}

	return skb;
@@ -256,7 +257,7 @@ static struct sk_buff *fq_codel_dequeue(struct Qdisc *sch) 
	prev_ecn_mark = q->cstats.ecn_mark;



	skb = codel_dequeue(sch, &q->cparams, &flow->cvars, &q->cstats,

			    dequeue, &q->backlogs[flow - q->flows]);

			    dequeue);



	flow->dropped += q->cstats.drop_count - prev_drop_count;

	flow->dropped += q->cstats.ecn_mark - prev_ecn_mark;