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: Eric 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: David S. Miller <davem@davemloft.net>

diff --git a/include/net/codel.h b/include/net/codel.h
index 7546517326b5c1dfd89776dc3d83f4ffe950cd52..550debfc240384f529562e3cc10cafcd342725f4 100644 (file)
--- a/include/net/codel.h
+++ b/include/net/codel.h
@@ -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;

diff --git a/net/sched/sch_codel.c b/net/sched/sch_codel.c
index 213ef60bced84f78fbc0c0882d1cde9fd42909ee..2f9ab17db85a59524556055bc5e53c5f2cab1a67 100644 (file)
--- a/net/sched/sch_codel.c
+++ b/net/sched/sch_codel.c
@@ -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.
         */

diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c
index 337ff204f27260e5d6d2c417e5228ebceeda4c9a..9fc1c62ec80e1ad56b760b2820c0c4f2e495d4a0 100644 (file)
--- a/net/sched/sch_fq_codel.c
+++ b/net/sched/sch_fq_codel.c
@@ -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 @@ begin:
        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;