target/linux/generic/patches-3.3/046-fq_codel-qdisc-backlog.patch

   1 From: Eric Dumazet <edumazet@google.com>
   2
   3 codel_should_drop() logic allows a packet being not dropped if queue
   4 size is under max packet size.
   5
   6 In fq_codel, we have two possible backlogs : The qdisc global one, and
   7 the flow local one.
   8
   9 The meaningful one for codel_should_drop() should be the global backlog,
  10 not the per flow one, so that thin flows can have a non zero drop/mark
  11 probability.
  12
  13 Signed-off-by: Eric Dumazet <edumazet@google.com>
  14 Cc: Dave Taht <dave.taht@bufferbloat.net>
  15 Cc: Kathleen Nichols <nichols@pollere.com>
  16 Cc: Van Jacobson <van@pollere.net>
  17 ---
  18  include/net/codel.h      |   15 +++++++--------
  19  net/sched/sch_codel.c    |    4 ++--
  20  net/sched/sch_fq_codel.c |    5 +++--
  21  3 files changed, 12 insertions(+), 12 deletions(-)
  22
  23 diff --git a/include/net/codel.h b/include/net/codel.h
  24 index 7546517..550debf 100644
  25 --- a/include/net/codel.h
  26 +++ b/include/net/codel.h
  27 @@ -205,7 +205,7 @@ static codel_time_t codel_control_law(codel_time_t t,
  28
  29
  30  static bool codel_should_drop(const struct sk_buff *skb,
  31 -                             unsigned int *backlog,
  32 +                             struct Qdisc *sch,
  33                               struct codel_vars *vars,
  34                               struct codel_params *params,
  35                               struct codel_stats *stats,
  36 @@ -219,13 +219,13 @@ static bool codel_should_drop(const struct sk_buff *skb,
  37         }
  38
  39         vars->ldelay = now - codel_get_enqueue_time(skb);
  40 -       *backlog -= qdisc_pkt_len(skb);
  41 +       sch->qstats.backlog -= qdisc_pkt_len(skb);
  42
  43         if (unlikely(qdisc_pkt_len(skb) > stats->maxpacket))
  44                 stats->maxpacket = qdisc_pkt_len(skb);
  45
  46         if (codel_time_before(vars->ldelay, params->target) ||
  47 -           *backlog <= stats->maxpacket) {
  48 +           sch->qstats.backlog <= stats->maxpacket) {
  49                 /* went below - stay below for at least interval */
  50                 vars->first_above_time = 0;
  51                 return false;
  52 @@ -249,8 +249,7 @@ static struct sk_buff *codel_dequeue(struct Qdisc *sch,
  53                                      struct codel_params *params,
  54                                      struct codel_vars *vars,
  55                                      struct codel_stats *stats,
  56 -                                    codel_skb_dequeue_t dequeue_func,
  57 -                                    u32 *backlog)
  58 +                                    codel_skb_dequeue_t dequeue_func)
  59  {
  60         struct sk_buff *skb = dequeue_func(vars, sch);
  61         codel_time_t now;
  62 @@ -261,7 +260,7 @@ static struct sk_buff *codel_dequeue(struct Qdisc *sch,
  63                 return skb;
  64         }
  65         now = codel_get_time();
  66 -       drop = codel_should_drop(skb, backlog, vars, params, stats, now);
  67 +       drop = codel_should_drop(skb, sch, vars, params, stats, now);
  68         if (vars->dropping) {
  69                 if (!drop) {
  70                         /* sojourn time below target - leave dropping state */
  71 @@ -292,7 +291,7 @@ static struct sk_buff *codel_dequeue(struct Qdisc *sch,
  72                                 qdisc_drop(skb, sch);
  73                                 stats->drop_count++;
  74                                 skb = dequeue_func(vars, sch);
  75 -                               if (!codel_should_drop(skb, backlog,
  76 +                               if (!codel_should_drop(skb, sch,
  77                                                        vars, params, stats, now)) {
  78                                         /* leave dropping state */
  79                                         vars->dropping = false;
  80 @@ -313,7 +312,7 @@ static struct sk_buff *codel_dequeue(struct Qdisc *sch,
  81                         stats->drop_count++;
  82
  83                         skb = dequeue_func(vars, sch);
  84 -                       drop = codel_should_drop(skb, backlog, vars, params,
  85 +                       drop = codel_should_drop(skb, sch, vars, params,
  86                                                  stats, now);
  87                 }
  88                 vars->dropping = true;
  89 diff --git a/net/sched/sch_codel.c b/net/sched/sch_codel.c
  90 index 213ef60..2f9ab17 100644
  91 --- a/net/sched/sch_codel.c
  92 +++ b/net/sched/sch_codel.c
  93 @@ -77,8 +77,8 @@ static struct sk_buff *codel_qdisc_dequeue(struct Qdisc *sch)
  94         struct codel_sched_data *q = qdisc_priv(sch);
  95         struct sk_buff *skb;
  96
  97 -       skb = codel_dequeue(sch, &q->params, &q->vars, &q->stats,
  98 -                           dequeue, &sch->qstats.backlog);
  99 +       skb = codel_dequeue(sch, &q->params, &q->vars, &q->stats, dequeue);
 100 +
 101         /* We cant call qdisc_tree_decrease_qlen() if our qlen is 0,
 102          * or HTB crashes. Defer it for next round.
 103          */
 104 diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c
 105 index 337ff20..9fc1c62 100644
 106 --- a/net/sched/sch_fq_codel.c
 107 +++ b/net/sched/sch_fq_codel.c
 108 @@ -217,13 +217,14 @@ static int fq_codel_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 109   */
 110  static struct sk_buff *dequeue(struct codel_vars *vars, struct Qdisc *sch)
 111  {
 112 +       struct fq_codel_sched_data *q = qdisc_priv(sch);
 113         struct fq_codel_flow *flow;
 114         struct sk_buff *skb = NULL;
 115
 116         flow = container_of(vars, struct fq_codel_flow, cvars);
 117         if (flow->head) {
 118                 skb = dequeue_head(flow);
 119 -               sch->qstats.backlog -= qdisc_pkt_len(skb);
 120 +               q->backlogs[flow - q->flows] -= qdisc_pkt_len(skb);
 121                 sch->q.qlen--;
 122         }
 123         return skb;
 124 @@ -256,7 +257,7 @@ begin:
 125         prev_ecn_mark = q->cstats.ecn_mark;
 126
 127         skb = codel_dequeue(sch, &q->cparams, &flow->cvars, &q->cstats,
 128 -                           dequeue, &q->backlogs[flow - q->flows]);
 129 +                           dequeue);
 130
 131         flow->dropped += q->cstats.drop_count - prev_drop_count;
 132         flow->dropped += q->cstats.ecn_mark - prev_ecn_mark;
 133