src/patches/linux-3.2-codel/0007-fq_codel-should-use-qdisc-backlog-as-threshold.patch

   1 From: Eric Dumazet <edumazet@google.com>
   2 Date: Wed, 16 May 2012 04:39:09 +0000
   3 Subject: [PATCH 7/7] fq_codel: should use qdisc backlog as threshold
   4
   5 commit 865ec5523dadbedefbc5710a68969f686a28d928 upstream.
   6
   7 codel_should_drop() logic allows a packet being not dropped if queue
   8 size is under max packet size.
   9
  10 In fq_codel, we have two possible backlogs : The qdisc global one, and
  11 the flow local one.
  12
  13 The meaningful one for codel_should_drop() should be the global backlog,
  14 not the per flow one, so that thin flows can have a non zero drop/mark
  15 probability.
  16
  17 Signed-off-by: Eric Dumazet <edumazet@google.com>
  18 Cc: Dave Taht <dave.taht@bufferbloat.net>
  19 Cc: Kathleen Nichols <nichols@pollere.com>
  20 Cc: Van Jacobson <van@pollere.net>
  21 Signed-off-by: David S. Miller <davem@davemloft.net>
  22 ---
  23  include/net/codel.h      |   15 +++++++--------
  24  net/sched/sch_codel.c    |    4 ++--
  25  net/sched/sch_fq_codel.c |    5 +++--
  26  3 files changed, 12 insertions(+), 12 deletions(-)
  27
  28 diff --git a/include/net/codel.h b/include/net/codel.h
  29 index 7546517..550debf 100644
  30 --- a/include/net/codel.h
  31 +++ b/include/net/codel.h
  32 @@ -205,7 +205,7 @@ static codel_time_t codel_control_law(codel_time_t t,
  33
  34
  35  static bool codel_should_drop(const struct sk_buff *skb,
  36 -                             unsigned int *backlog,
  37 +                             struct Qdisc *sch,
  38                               struct codel_vars *vars,
  39                               struct codel_params *params,
  40                               struct codel_stats *stats,
  41 @@ -219,13 +219,13 @@ static bool codel_should_drop(const struct sk_buff *skb,
  42         }
  43
  44         vars->ldelay = now - codel_get_enqueue_time(skb);
  45 -       *backlog -= qdisc_pkt_len(skb);
  46 +       sch->qstats.backlog -= qdisc_pkt_len(skb);
  47
  48         if (unlikely(qdisc_pkt_len(skb) > stats->maxpacket))
  49                 stats->maxpacket = qdisc_pkt_len(skb);
  50
  51         if (codel_time_before(vars->ldelay, params->target) ||
  52 -           *backlog <= stats->maxpacket) {
  53 +           sch->qstats.backlog <= stats->maxpacket) {
  54                 /* went below - stay below for at least interval */
  55                 vars->first_above_time = 0;
  56                 return false;
  57 @@ -249,8 +249,7 @@ static struct sk_buff *codel_dequeue(struct Qdisc *sch,
  58                                      struct codel_params *params,
  59                                      struct codel_vars *vars,
  60                                      struct codel_stats *stats,
  61 -                                    codel_skb_dequeue_t dequeue_func,
  62 -                                    u32 *backlog)
  63 +                                    codel_skb_dequeue_t dequeue_func)
  64  {
  65         struct sk_buff *skb = dequeue_func(vars, sch);
  66         codel_time_t now;
  67 @@ -261,7 +260,7 @@ static struct sk_buff *codel_dequeue(struct Qdisc *sch,
  68                 return skb;
  69         }
  70         now = codel_get_time();
  71 -       drop = codel_should_drop(skb, backlog, vars, params, stats, now);
  72 +       drop = codel_should_drop(skb, sch, vars, params, stats, now);
  73         if (vars->dropping) {
  74                 if (!drop) {
  75                         /* sojourn time below target - leave dropping state */
  76 @@ -292,7 +291,7 @@ static struct sk_buff *codel_dequeue(struct Qdisc *sch,
  77                                 qdisc_drop(skb, sch);
  78                                 stats->drop_count++;
  79                                 skb = dequeue_func(vars, sch);
  80 -                               if (!codel_should_drop(skb, backlog,
  81 +                               if (!codel_should_drop(skb, sch,
  82                                                        vars, params, stats, now)) {
  83                                         /* leave dropping state */
  84                                         vars->dropping = false;
  85 @@ -313,7 +312,7 @@ static struct sk_buff *codel_dequeue(struct Qdisc *sch,
  86                         stats->drop_count++;
  87
  88                         skb = dequeue_func(vars, sch);
  89 -                       drop = codel_should_drop(skb, backlog, vars, params,
  90 +                       drop = codel_should_drop(skb, sch, vars, params,
  91                                                  stats, now);
  92                 }
  93                 vars->dropping = true;
  94 diff --git a/net/sched/sch_codel.c b/net/sched/sch_codel.c
  95 index 213ef60..2f9ab17 100644
  96 --- a/net/sched/sch_codel.c
  97 +++ b/net/sched/sch_codel.c
  98 @@ -77,8 +77,8 @@ static struct sk_buff *codel_qdisc_dequeue(struct Qdisc *sch)
  99         struct codel_sched_data *q = qdisc_priv(sch);
 100         struct sk_buff *skb;
 101
 102 -       skb = codel_dequeue(sch, &q->params, &q->vars, &q->stats,
 103 -                           dequeue, &sch->qstats.backlog);
 104 +       skb = codel_dequeue(sch, &q->params, &q->vars, &q->stats, dequeue);
 105 +
 106         /* We cant call qdisc_tree_decrease_qlen() if our qlen is 0,
 107          * or HTB crashes. Defer it for next round.
 108          */
 109 diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c
 110 index 337ff20..9fc1c62 100644
 111 --- a/net/sched/sch_fq_codel.c
 112 +++ b/net/sched/sch_fq_codel.c
 113 @@ -217,13 +217,14 @@ static int fq_codel_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 114   */
 115  static struct sk_buff *dequeue(struct codel_vars *vars, struct Qdisc *sch)
 116  {
 117 +       struct fq_codel_sched_data *q = qdisc_priv(sch);
 118         struct fq_codel_flow *flow;
 119         struct sk_buff *skb = NULL;
 120
 121         flow = container_of(vars, struct fq_codel_flow, cvars);
 122         if (flow->head) {
 123                 skb = dequeue_head(flow);
 124 -               sch->qstats.backlog -= qdisc_pkt_len(skb);
 125 +               q->backlogs[flow - q->flows] -= qdisc_pkt_len(skb);
 126                 sch->q.qlen--;
 127         }
 128         return skb;
 129 @@ -256,7 +257,7 @@ begin:
 130         prev_ecn_mark = q->cstats.ecn_mark;
 131
 132         skb = codel_dequeue(sch, &q->cparams, &flow->cvars, &q->cstats,
 133 -                           dequeue, &q->backlogs[flow - q->flows]);
 134 +                           dequeue);
 135
 136         flow->dropped += q->cstats.drop_count - prev_drop_count;
 137         flow->dropped += q->cstats.ecn_mark - prev_ecn_mark;
 138 --
 139 1.7.10
 140