mac80211: add standard deviation to Minstrel stats
This patch adds the statistical descriptor "standard deviation"
to better describe the current properties of Minstrel and
Minstrel-HTs success probability distribution. The standard
deviation (SD) is calculated as exponential weighted moving
standard deviation (EWMSD) and its current value is added as
new column in all rc_stats (in debugfs).
Signed-off-by: Thomas Huehn <thomas@net.t-labs.tu-berlin.de>
Acked-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/rc80211_minstrel.c b/net/mac80211/rc80211_minstrel.c
index c4a3477..247552a 100644
--- a/net/mac80211/rc80211_minstrel.c
+++ b/net/mac80211/rc80211_minstrel.c
@@ -153,7 +153,7 @@
}
/*
-* Recalculate success probabilities and counters for a given rate using EWMA
+* Recalculate statistics and counters of a given rate
*/
void
minstrel_calc_rate_stats(struct minstrel_rate_stats *mrs)
@@ -161,11 +161,20 @@
if (unlikely(mrs->attempts > 0)) {
mrs->sample_skipped = 0;
mrs->cur_prob = MINSTREL_FRAC(mrs->success, mrs->attempts);
- if (unlikely(!mrs->att_hist))
+ if (unlikely(!mrs->att_hist)) {
mrs->prob_ewma = mrs->cur_prob;
- else
+ } else {
+ /* update exponential weighted moving variance */
+ mrs->prob_ewmsd = minstrel_ewmsd(mrs->prob_ewmsd,
+ mrs->cur_prob,
+ mrs->prob_ewma,
+ EWMA_LEVEL);
+
+ /*update exponential weighted moving avarage */
mrs->prob_ewma = minstrel_ewma(mrs->prob_ewma,
- mrs->cur_prob, EWMA_LEVEL);
+ mrs->cur_prob,
+ EWMA_LEVEL);
+ }
mrs->att_hist += mrs->attempts;
mrs->succ_hist += mrs->success;
} else {
@@ -193,7 +202,7 @@
struct minstrel_rate_stats *mrs = &mi->r[i].stats;
struct minstrel_rate_stats *tmp_mrs = &mi->r[tmp_prob_rate].stats;
- /* Update success probabilities per rate */
+ /* Update statistics of success probability per rate */
minstrel_calc_rate_stats(mrs);
/* Sample less often below the 10% chance of success.