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mac80211: add minstrel performance improvements

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Reduce fluctuations in rate selection / statistics

Signed-off-by: Felix Fietkau <nbd@nbd.name>
This commit is contained in:
Felix Fietkau 2021-02-06 16:46:56 +01:00
parent b6066846ad
commit 072bfe2113
2 changed files with 181 additions and 0 deletions
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30
package/kernel/mac80211/patches/subsys/354-mac80211-minstrel_ht-reduce-fluctuations-in-rate-pro.patch Normal file
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From: Felix Fietkau <nbd@nbd.name>
Date: Sat, 6 Feb 2021 16:08:01 +0100
Subject: [PATCH] mac80211: minstrel_ht: reduce fluctuations in rate
probability stats
In some scenarios when there is a lot of fluctuation in packet error rates,
rate switching can be amplified when the statistics get skewed by time slots
with very few tries.
Make the input data to the moving average more smooth by adding the
success/attempts count from the last stats window as well. This has the
advantage of smoothing the data without introducing any extra lag to sampling
rates.
This significantly improves rate stability on a strong test link subjected to
periodic noise bursts generated with a SDR
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
--- a/net/mac80211/rc80211_minstrel_ht.c
+++ b/net/mac80211/rc80211_minstrel_ht.c
@@ -700,7 +700,8 @@ minstrel_ht_calc_rate_stats(struct minst
unsigned int cur_prob;
if (unlikely(mrs->attempts > 0)) {
- cur_prob = MINSTREL_FRAC(mrs->success, mrs->attempts);
+ cur_prob = MINSTREL_FRAC(mrs->success + mrs->last_success,
+ mrs->attempts + mrs->last_attempts);
minstrel_filter_avg_add(&mrs->prob_avg,
&mrs->prob_avg_1, cur_prob);
mrs->att_hist += mrs->attempts;

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package/kernel/mac80211/patches/subsys/355-mac80211-minstrel_ht-rework-rate-downgrade-code-and-.patch Normal file
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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
@@ -511,6 +511,14 @@ 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);
@@ -532,11 +540,6 @@ 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;
@@ -594,40 +597,6 @@ 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)
@@ -1111,8 +1080,6 @@ 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
@@ -1157,7 +1124,7 @@ 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;
@@ -1172,11 +1139,7 @@ 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;
}
}
@@ -1210,7 +1173,7 @@ 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;
@@ -1256,18 +1219,13 @@ 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;
}
}