+++ /dev/null
-From: Felix Fietkau <nbd@nbd.name>
-Date: Sat, 6 Feb 2021 16:33:14 +0100
-Subject: [PATCH] mac80211: minstrel_ht: rework rate downgrade code and
- max_prob rate selection
-
-The current fallback code for fast rate switching on potentially failing rates
-is triggering too often if there is some strong noise on the channel. This can
-lead to wild fluctuations in the rate selection.
-Additionally, switching down to max_prob_rate can create a significant gap down
-in throughput, especially when using only 2 spatial streams, because max_prob_rate
-is limited to using fewer streams than the max_tp rates.
-In order to improve throughput without reducing reliability too much, use the
-rate downgrade code for the max_prob_rate only, and allow the non-downgraded
-max_prob_rate to use as many spatial streams as the max_tp rates
-
-Signed-off-by: Felix Fietkau <nbd@nbd.name>
----
-
---- a/net/mac80211/rc80211_minstrel_ht.c
-+++ b/net/mac80211/rc80211_minstrel_ht.c
-@@ -514,6 +514,14 @@ minstrel_ht_set_best_prob_rate(struct mi
- int cur_tp_avg, cur_group, cur_idx;
- int max_gpr_group, max_gpr_idx;
- int max_gpr_tp_avg, max_gpr_prob;
-+ int min_dur;
-+
-+ min_dur = max(minstrel_get_duration(mi->max_tp_rate[0]),
-+ minstrel_get_duration(mi->max_tp_rate[1]));
-+
-+ /* make the rate at least 18% slower than max tp rates */
-+ if (minstrel_get_duration(index) <= min_dur * 19 / 16)
-+ return;
-
- cur_group = MI_RATE_GROUP(index);
- cur_idx = MI_RATE_IDX(index);
-@@ -535,11 +543,6 @@ minstrel_ht_set_best_prob_rate(struct mi
- !minstrel_ht_is_legacy_group(max_tp_group))
- return;
-
-- /* skip rates faster than max tp rate with lower prob */
-- if (minstrel_get_duration(mi->max_tp_rate[0]) > minstrel_get_duration(index) &&
-- mrs->prob_avg < max_tp_prob)
-- return;
--
- max_gpr_group = MI_RATE_GROUP(mg->max_group_prob_rate);
- max_gpr_idx = MI_RATE_IDX(mg->max_group_prob_rate);
- max_gpr_prob = mi->groups[max_gpr_group].rates[max_gpr_idx].prob_avg;
-@@ -597,40 +600,6 @@ minstrel_ht_assign_best_tp_rates(struct
-
- }
-
--/*
-- * Try to increase robustness of max_prob rate by decrease number of
-- * streams if possible.
-- */
--static inline void
--minstrel_ht_prob_rate_reduce_streams(struct minstrel_ht_sta *mi)
--{
-- struct minstrel_mcs_group_data *mg;
-- int tmp_max_streams, group, tmp_idx, tmp_prob;
-- int tmp_tp = 0;
--
-- if (!mi->sta->ht_cap.ht_supported)
-- return;
--
-- group = MI_RATE_GROUP(mi->max_tp_rate[0]);
-- tmp_max_streams = minstrel_mcs_groups[group].streams;
-- for (group = 0; group < ARRAY_SIZE(minstrel_mcs_groups); group++) {
-- mg = &mi->groups[group];
-- if (!mi->supported[group] || group == MINSTREL_CCK_GROUP)
-- continue;
--
-- tmp_idx = MI_RATE_IDX(mg->max_group_prob_rate);
-- tmp_prob = mi->groups[group].rates[tmp_idx].prob_avg;
--
-- if (tmp_tp < minstrel_ht_get_tp_avg(mi, group, tmp_idx, tmp_prob) &&
-- (minstrel_mcs_groups[group].streams < tmp_max_streams)) {
-- mi->max_prob_rate = mg->max_group_prob_rate;
-- tmp_tp = minstrel_ht_get_tp_avg(mi, group,
-- tmp_idx,
-- tmp_prob);
-- }
-- }
--}
--
- static u16
- __minstrel_ht_get_sample_rate(struct minstrel_ht_sta *mi,
- enum minstrel_sample_type type)
-@@ -1110,8 +1079,6 @@ minstrel_ht_update_stats(struct minstrel
-
- mi->max_prob_rate = tmp_max_prob_rate;
-
-- /* Try to increase robustness of max_prob_rate*/
-- minstrel_ht_prob_rate_reduce_streams(mi);
- minstrel_ht_refill_sample_rates(mi);
-
- #ifdef CPTCFG_MAC80211_DEBUGFS
-@@ -1156,7 +1123,7 @@ minstrel_ht_txstat_valid(struct minstrel
- }
-
- static void
--minstrel_downgrade_rate(struct minstrel_ht_sta *mi, u16 *idx, bool primary)
-+minstrel_downgrade_prob_rate(struct minstrel_ht_sta *mi, u16 *idx)
- {
- int group, orig_group;
-
-@@ -1171,11 +1138,7 @@ minstrel_downgrade_rate(struct minstrel_
- minstrel_mcs_groups[orig_group].streams)
- continue;
-
-- if (primary)
-- *idx = mi->groups[group].max_group_tp_rate[0];
-- else
-- *idx = mi->groups[group].max_group_tp_rate[1];
-- break;
-+ *idx = mi->groups[group].max_group_prob_rate;
- }
- }
-
-@@ -1186,7 +1149,7 @@ minstrel_ht_tx_status(void *priv, struct
- struct ieee80211_tx_info *info = st->info;
- struct minstrel_ht_sta *mi = priv_sta;
- struct ieee80211_tx_rate *ar = info->status.rates;
-- struct minstrel_rate_stats *rate, *rate2;
-+ struct minstrel_rate_stats *rate;
- struct minstrel_priv *mp = priv;
- u32 update_interval = mp->update_interval;
- bool last, update = false;
-@@ -1236,18 +1199,13 @@ minstrel_ht_tx_status(void *priv, struct
- /*
- * check for sudden death of spatial multiplexing,
- * downgrade to a lower number of streams if necessary.
-+ * only do this for the max_prob_rate to prevent spurious
-+ * rate fluctuations when the link changes suddenly
- */
-- rate = minstrel_get_ratestats(mi, mi->max_tp_rate[0]);
-+ rate = minstrel_get_ratestats(mi, mi->max_prob_rate);
- if (rate->attempts > 30 &&
- rate->success < rate->attempts / 4) {
-- minstrel_downgrade_rate(mi, &mi->max_tp_rate[0], true);
-- update = true;
-- }
--
-- rate2 = minstrel_get_ratestats(mi, mi->max_tp_rate[1]);
-- if (rate2->attempts > 30 &&
-- rate2->success < rate2->attempts / 4) {
-- minstrel_downgrade_rate(mi, &mi->max_tp_rate[1], false);
-+ minstrel_downgrade_prob_rate(mi, &mi->max_prob_rate);
- update = true;
- }
- }
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