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>

3 files changed, 12 insertions, 12 deletions

diff --git a/include/net/codel.h b/include/net/codel.h
index 7546517326b5..550debfc2403 100644
--- 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 213ef60bced8..2f9ab17db85a 100644
--- 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 337ff204f272..9fc1c62ec80e 100644
--- 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;