package/kernel/mac80211/patches/343-mac80211-minstrel_ht-improve-sample-rate-skip-logic.patch

   1 From: Felix Fietkau <nbd@openwrt.org>
   2 Date: Thu, 3 Mar 2016 23:20:06 +0100
   3 Subject: [PATCH] mac80211: minstrel_ht: improve sample rate skip logic
   4
   5 There were a few issues that were slowing down the process of finding
   6 the optimal rate, especially on devices with multi-rate retry
   7 limitations:
   8
   9 When max_tp_rate[0] was slower than max_tp_rate[1], the code did not
  10 sample max_tp_rate[1], which would often allow it to switch places with
  11 max_tp_rate[0] (e.g. if only the first sampling attempts were bad, but the
  12 rate is otherwise good).
  13
  14 Also, sample attempts of rates between max_tp_rate[0] and [1] were being
  15 ignored in this case, because the code only checked if the rate was
  16 slower than [1].
  17
  18 Fix this by checking against the fastest / second fastest max_tp_rate
  19 instead of assuming a specific order between the two.
  20
  21 In my tests this patch significantly reduces the time until minstrel_ht
  22 finds the optimal rate right after assoc
  23
  24 Signed-off-by: Felix Fietkau <nbd@openwrt.org>
  25 ---
  26
  27 --- a/net/mac80211/rc80211_minstrel_ht.c
  28 +++ b/net/mac80211/rc80211_minstrel_ht.c
  29 @@ -958,6 +958,7 @@ minstrel_get_sample_rate(struct minstrel
  30         struct minstrel_rate_stats *mrs;
  31         struct minstrel_mcs_group_data *mg;
  32         unsigned int sample_dur, sample_group, cur_max_tp_streams;
  33 +       int tp_rate1, tp_rate2;
  34         int sample_idx = 0;
  35
  36         if (mi->sample_wait > 0) {
  37 @@ -979,14 +980,22 @@ minstrel_get_sample_rate(struct minstrel
  38         mrs = &mg->rates[sample_idx];
  39         sample_idx += sample_group * MCS_GROUP_RATES;
  40
  41 +       /* Set tp_rate1, tp_rate2 to the highest / second highest max_tp_rate */
  42 +       if (minstrel_get_duration(mi->max_tp_rate[0]) >
  43 +           minstrel_get_duration(mi->max_tp_rate[1])) {
  44 +               tp_rate1 = mi->max_tp_rate[1];
  45 +               tp_rate2 = mi->max_tp_rate[0];
  46 +       } else {
  47 +               tp_rate1 = mi->max_tp_rate[0];
  48 +               tp_rate2 = mi->max_tp_rate[1];
  49 +       }
  50 +
  51         /*
  52          * Sampling might add some overhead (RTS, no aggregation)
  53 -        * to the frame. Hence, don't use sampling for the currently
  54 -        * used rates.
  55 +        * to the frame. Hence, don't use sampling for the highest currently
  56 +        * used highest throughput or probability rate.
  57          */
  58 -       if (sample_idx == mi->max_tp_rate[0] ||
  59 -           sample_idx == mi->max_tp_rate[1] ||
  60 -           sample_idx == mi->max_prob_rate)
  61 +       if (sample_idx == mi->max_tp_rate[0] || sample_idx == mi->max_prob_rate)
  62                 return -1;
  63
  64         /*
  65 @@ -1001,10 +1010,10 @@ minstrel_get_sample_rate(struct minstrel
  66          * if the link is working perfectly.
  67          */
  68
  69 -       cur_max_tp_streams = minstrel_mcs_groups[mi->max_tp_rate[0] /
  70 +       cur_max_tp_streams = minstrel_mcs_groups[tp_rate1 /
  71                 MCS_GROUP_RATES].streams;
  72         sample_dur = minstrel_get_duration(sample_idx);
  73 -       if (sample_dur >= minstrel_get_duration(mi->max_tp_rate[1]) &&
  74 +       if (sample_dur >= minstrel_get_duration(tp_rate2) &&
  75             (cur_max_tp_streams - 1 <
  76              minstrel_mcs_groups[sample_group].streams ||
  77              sample_dur >= minstrel_get_duration(mi->max_prob_rate))) {