package/kernel/mac80211/patches/subsys/355-mac80211-minstrel_ht-rework-rate-downgrade-code-and-.patch

   1 From: Felix Fietkau <nbd@nbd.name>
   2 Date: Sat, 6 Feb 2021 16:33:14 +0100
   3 Subject: [PATCH] mac80211: minstrel_ht: rework rate downgrade code and
   4  max_prob rate selection
   5
   6 The current fallback code for fast rate switching on potentially failing rates
   7 is triggering too often if there is some strong noise on the channel. This can
   8 lead to wild fluctuations in the rate selection.
   9 Additionally, switching down to max_prob_rate can create a significant gap down
  10 in throughput, especially when using only 2 spatial streams, because max_prob_rate
  11 is limited to using fewer streams than the max_tp rates.
  12 In order to improve throughput without reducing reliability too much, use the
  13 rate downgrade code for the max_prob_rate only, and allow the non-downgraded
  14 max_prob_rate to use as many spatial streams as the max_tp rates
  15
  16 Signed-off-by: Felix Fietkau <nbd@nbd.name>
  17 ---
  18
  19 --- a/net/mac80211/rc80211_minstrel_ht.c
  20 +++ b/net/mac80211/rc80211_minstrel_ht.c
  21 @@ -511,6 +511,14 @@ minstrel_ht_set_best_prob_rate(struct mi
  22         int cur_tp_avg, cur_group, cur_idx;
  23         int max_gpr_group, max_gpr_idx;
  24         int max_gpr_tp_avg, max_gpr_prob;
  25 +       int min_dur;
  26 +
  27 +       min_dur = max(minstrel_get_duration(mi->max_tp_rate[0]),
  28 +                     minstrel_get_duration(mi->max_tp_rate[1]));
  29 +
  30 +       /* make the rate at least 18% slower than max tp rates */
  31 +       if (minstrel_get_duration(index) <= min_dur * 19 / 16)
  32 +               return;
  33
  34         cur_group = MI_RATE_GROUP(index);
  35         cur_idx = MI_RATE_IDX(index);
  36 @@ -532,11 +540,6 @@ minstrel_ht_set_best_prob_rate(struct mi
  37             !minstrel_ht_is_legacy_group(max_tp_group))
  38                 return;
  39
  40 -       /* skip rates faster than max tp rate with lower prob */
  41 -       if (minstrel_get_duration(mi->max_tp_rate[0]) > minstrel_get_duration(index) &&
  42 -           mrs->prob_avg < max_tp_prob)
  43 -               return;
  44 -
  45         max_gpr_group = MI_RATE_GROUP(mg->max_group_prob_rate);
  46         max_gpr_idx = MI_RATE_IDX(mg->max_group_prob_rate);
  47         max_gpr_prob = mi->groups[max_gpr_group].rates[max_gpr_idx].prob_avg;
  48 @@ -594,40 +597,6 @@ minstrel_ht_assign_best_tp_rates(struct
  49
  50  }
  51
  52 -/*
  53 - * Try to increase robustness of max_prob rate by decrease number of
  54 - * streams if possible.
  55 - */
  56 -static inline void
  57 -minstrel_ht_prob_rate_reduce_streams(struct minstrel_ht_sta *mi)
  58 -{
  59 -       struct minstrel_mcs_group_data *mg;
  60 -       int tmp_max_streams, group, tmp_idx, tmp_prob;
  61 -       int tmp_tp = 0;
  62 -
  63 -       if (!mi->sta->ht_cap.ht_supported)
  64 -               return;
  65 -
  66 -       group = MI_RATE_GROUP(mi->max_tp_rate[0]);
  67 -       tmp_max_streams = minstrel_mcs_groups[group].streams;
  68 -       for (group = 0; group < ARRAY_SIZE(minstrel_mcs_groups); group++) {
  69 -               mg = &mi->groups[group];
  70 -               if (!mi->supported[group] || group == MINSTREL_CCK_GROUP)
  71 -                       continue;
  72 -
  73 -               tmp_idx = MI_RATE_IDX(mg->max_group_prob_rate);
  74 -               tmp_prob = mi->groups[group].rates[tmp_idx].prob_avg;
  75 -
  76 -               if (tmp_tp < minstrel_ht_get_tp_avg(mi, group, tmp_idx, tmp_prob) &&
  77 -                  (minstrel_mcs_groups[group].streams < tmp_max_streams)) {
  78 -                               mi->max_prob_rate = mg->max_group_prob_rate;
  79 -                               tmp_tp = minstrel_ht_get_tp_avg(mi, group,
  80 -                                                               tmp_idx,
  81 -                                                               tmp_prob);
  82 -               }
  83 -       }
  84 -}
  85 -
  86  static u16
  87  __minstrel_ht_get_sample_rate(struct minstrel_ht_sta *mi,
  88                               enum minstrel_sample_type type)
  89 @@ -1111,8 +1080,6 @@ minstrel_ht_update_stats(struct minstrel
  90
  91         mi->max_prob_rate = tmp_max_prob_rate;
  92
  93 -       /* Try to increase robustness of max_prob_rate*/
  94 -       minstrel_ht_prob_rate_reduce_streams(mi);
  95         minstrel_ht_refill_sample_rates(mi);
  96
  97  #ifdef CPTCFG_MAC80211_DEBUGFS
  98 @@ -1157,7 +1124,7 @@ minstrel_ht_txstat_valid(struct minstrel
  99  }
 100
 101  static void
 102 -minstrel_downgrade_rate(struct minstrel_ht_sta *mi, u16 *idx, bool primary)
 103 +minstrel_downgrade_prob_rate(struct minstrel_ht_sta *mi, u16 *idx)
 104  {
 105         int group, orig_group;
 106
 107 @@ -1172,11 +1139,7 @@ minstrel_downgrade_rate(struct minstrel_
 108                     minstrel_mcs_groups[orig_group].streams)
 109                         continue;
 110
 111 -               if (primary)
 112 -                       *idx = mi->groups[group].max_group_tp_rate[0];
 113 -               else
 114 -                       *idx = mi->groups[group].max_group_tp_rate[1];
 115 -               break;
 116 +               *idx = mi->groups[group].max_group_prob_rate;
 117         }
 118  }
 119
 120 @@ -1210,7 +1173,7 @@ minstrel_ht_tx_status(void *priv, struct
 121         struct ieee80211_tx_info *info = st->info;
 122         struct minstrel_ht_sta *mi = priv_sta;
 123         struct ieee80211_tx_rate *ar = info->status.rates;
 124 -       struct minstrel_rate_stats *rate, *rate2;
 125 +       struct minstrel_rate_stats *rate;
 126         struct minstrel_priv *mp = priv;
 127         u32 update_interval = mp->update_interval;
 128         bool last, update = false;
 129 @@ -1256,18 +1219,13 @@ minstrel_ht_tx_status(void *priv, struct
 130                 /*
 131                  * check for sudden death of spatial multiplexing,
 132                  * downgrade to a lower number of streams if necessary.
 133 +                * only do this for the max_prob_rate to prevent spurious
 134 +                * rate fluctuations when the link changes suddenly
 135                  */
 136 -               rate = minstrel_get_ratestats(mi, mi->max_tp_rate[0]);
 137 +               rate = minstrel_get_ratestats(mi, mi->max_prob_rate);
 138                 if (rate->attempts > 30 &&
 139                     rate->success < rate->attempts / 4) {
 140 -                       minstrel_downgrade_rate(mi, &mi->max_tp_rate[0], true);
 141 -                       update = true;
 142 -               }
 143 -
 144 -               rate2 = minstrel_get_ratestats(mi, mi->max_tp_rate[1]);
 145 -               if (rate2->attempts > 30 &&
 146 -                   rate2->success < rate2->attempts / 4) {
 147 -                       minstrel_downgrade_rate(mi, &mi->max_tp_rate[1], false);
 148 +                       minstrel_downgrade_prob_rate(mi, &mi->max_prob_rate);
 149                         update = true;
 150                 }
 151         }