package/kernel/mac80211/patches/subsys/313-mac80211-improve-AQL-aggregation-estimation-for-low-.patch

   1 From: Felix Fietkau <nbd@nbd.name>
   2 Date: Wed, 12 Aug 2020 17:07:10 +0200
   3 Subject: [PATCH] mac80211: improve AQL aggregation estimation for low data
   4  rates
   5
   6 Links with low data rates use much smaller aggregates and are much more
   7 sensitive to latency added by bufferbloat.
   8 Tune the assumed aggregation length based on the tx rate duration.
   9
  10 Signed-off-by: Felix Fietkau <nbd@nbd.name>
  11 ---
  12
  13 --- a/net/mac80211/airtime.c
  14 +++ b/net/mac80211/airtime.c
  15 @@ -647,27 +647,41 @@ u32 ieee80211_calc_expected_tx_airtime(s
  16         if (pubsta) {
  17                 struct sta_info *sta = container_of(pubsta, struct sta_info,
  18                                                     sta);
  19 +               struct ieee80211_rx_status stat;
  20                 struct ieee80211_tx_rate *rate = &sta->tx_stats.last_rate;
  21                 struct rate_info *ri = &sta->tx_stats.last_rate_info;
  22 -               u32 airtime;
  23 +               u32 duration, overhead;
  24 +               u8 agg_shift;
  25
  26 -               if (!(rate->flags & (IEEE80211_TX_RC_VHT_MCS |
  27 -                                    IEEE80211_TX_RC_MCS)))
  28 -                       ampdu = false;
  29 +               if (ieee80211_fill_rx_status(&stat, hw, rate, ri, band, len))
  30 +                       return 0;
  31
  32 +               if (stat.encoding == RX_ENC_LEGACY || !ampdu)
  33 +                       return ieee80211_calc_rx_airtime(hw, &stat, len);
  34 +
  35 +               duration = ieee80211_get_rate_duration(hw, &stat, &overhead);
  36                 /*
  37                  * Assume that HT/VHT transmission on any AC except VO will
  38                  * use aggregation. Since we don't have reliable reporting
  39 -                * of aggregation length, assume an average of 16.
  40 +                * of aggregation length, assume an average size based on the
  41 +                * tx rate.
  42                  * This will not be very accurate, but much better than simply
  43 -                * assuming un-aggregated tx.
  44 +                * assuming un-aggregated tx in all cases.
  45                  */
  46 -               airtime = ieee80211_calc_tx_airtime_rate(hw, rate, ri, band,
  47 -                                                        ampdu ? len * 16 : len);
  48 -               if (ampdu)
  49 -                       airtime /= 16;
  50 +               if (duration > 400) /* <= VHT20 MCS2 1S */
  51 +                       agg_shift = 1;
  52 +               else if (duration > 250) /* <= VHT20 MCS3 1S or MCS1 2S */
  53 +                       agg_shift = 2;
  54 +               else if (duration > 150) /* <= VHT20 MCS5 1S or MCS3 2S */
  55 +                       agg_shift = 3;
  56 +               else
  57 +                       agg_shift = 4;
  58
  59 -               return airtime;
  60 +               duration *= len;
  61 +               duration /= AVG_PKT_SIZE;
  62 +               duration /= 1024;
  63 +
  64 +               return duration + (overhead >> agg_shift);
  65         }
  66
  67         if (!conf)