diff options
| author | Thomas Huehn <thomas@net.t-labs.tu-berlin.de> | 2015-03-24 21:09:43 +0100 |
|---|---|---|
| committer | Johannes Berg <johannes.berg@intel.com> | 2015-04-01 20:44:33 +0200 |
| commit | 5f919abc76fc3de1e5965ea03c925f7563c7fc15 (patch) | |
| tree | 8ed67f827d3b66cbfb140c66d8cd2d0f115633a6 /net/mac80211/rc80211_minstrel.h | |
| parent | mac80211: reduce calculation costs of EWMA (diff) | |
| download | linux-5f919abc76fc3de1e5965ea03c925f7563c7fc15.tar.xz linux-5f919abc76fc3de1e5965ea03c925f7563c7fc15.zip | |
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>
Diffstat (limited to 'net/mac80211/rc80211_minstrel.h')
| -rw-r--r-- | net/mac80211/rc80211_minstrel.h | 22 |
1 files changed, 21 insertions, 1 deletions
diff --git a/net/mac80211/rc80211_minstrel.h b/net/mac80211/rc80211_minstrel.h index 9c85a610b57b..c230bbe93262 100644 --- a/net/mac80211/rc80211_minstrel.h +++ b/net/mac80211/rc80211_minstrel.h @@ -35,6 +35,24 @@ minstrel_ewma(int old, int new, int weight) return old + incr; } +/* + * Perform EWMSD (Exponentially Weighted Moving Standard Deviation) calculation + */ +static inline int +minstrel_ewmsd(int old_ewmsd, int cur_prob, int prob_ewma, int weight) +{ + int diff, incr, tmp_var; + + /* calculate exponential weighted moving variance */ + diff = MINSTREL_TRUNC((cur_prob - prob_ewma) * 1000000); + incr = (EWMA_DIV - weight) * diff / EWMA_DIV; + tmp_var = old_ewmsd * old_ewmsd; + tmp_var = weight * (tmp_var + diff * incr / 1000000) / EWMA_DIV; + + /* return standard deviation */ + return (u16) int_sqrt(tmp_var); +} + struct minstrel_rate_stats { /* current / last sampling period attempts/success counters */ u16 attempts, last_attempts; @@ -45,9 +63,11 @@ struct minstrel_rate_stats { /* statistis of packet delivery probability * cur_prob - current prob within last update intervall - * prob_ewma - exponential weighted moving average of prob */ + * prob_ewma - exponential weighted moving average of prob + * prob_ewmsd - exp. weighted moving standard deviation of prob */ unsigned int cur_prob; unsigned int prob_ewma; + u16 prob_ewmsd; /* maximum retry counts */ u8 retry_count; |