mac80211: add minstrel performance improvements

Reduce fluctuations in rate selection / statistics

Signed-off-by: Felix Fietkau <nbd@nbd.name>

1 files changed, 30 insertions, 0 deletions

diff --git a/package/kernel/mac80211/patches/subsys/354-mac80211-minstrel_ht-reduce-fluctuations-in-rate-pro.patch b/package/kernel/mac80211/patches/subsys/354-mac80211-minstrel_ht-reduce-fluctuations-in-rate-pro.patch
new file mode 100644
index 0000000000..16bcbc2ef9
--- /dev/null
+++ b/package/kernel/mac80211/patches/subsys/354-mac80211-minstrel_ht-reduce-fluctuations-in-rate-pro.patch
@@ -0,0 +1,30 @@
+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;