| 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 |
| @@ -580,6 +580,14 @@ 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); |
| @@ -601,11 +609,6 @@ 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; |
| @@ -663,40 +666,6 @@ 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->deflink.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) |
| @@ -1176,8 +1145,6 @@ 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 |
| @@ -1256,7 +1223,7 @@ minstrel_ht_ri_txstat_valid(struct minst |
| } |
| |
| 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; |
| |
| @@ -1271,11 +1238,7 @@ 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; |
| } |
| } |
| |
| @@ -1286,7 +1249,7 @@ 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; |
| @@ -1354,18 +1317,13 @@ 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; |
| } |
| } |