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@xxxxxxxxxxxxxxxxxxxxxxx>
---
net/mac80211/rc80211_minstrel.c | 19 ++++++++++++++-----
net/mac80211/rc80211_minstrel.h | 22 +++++++++++++++++++++-
net/mac80211/rc80211_minstrel_debugfs.c | 19 ++++++++++++-------
net/mac80211/rc80211_minstrel_ht_debugfs.c | 14 +++++++++-----
4 files changed, 56 insertions(+), 18 deletions(-)
diff --git a/net/mac80211/rc80211_minstrel.c b/net/mac80211/rc80211_minstrel.c
index c2afe51..30512d0 100644
--- a/net/mac80211/rc80211_minstrel.c
+++ b/net/mac80211/rc80211_minstrel.c
@@ -156,7 +156,7 @@ minstrel_update_rates(struct minstrel_priv *mp, struct minstrel_sta_info *mi)
}
/*
-* 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)
@@ -164,11 +164,20 @@ minstrel_calc_rate_stats(struct minstrel_rate_stats *mrs)
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 {
@@ -195,7 +204,7 @@ minstrel_update_stats(struct minstrel_priv *mp, struct minstrel_sta_info *mi)
struct minstrel_rate *mr = &mi->r[i];
struct minstrel_rate_stats *mrs = &mi->r[i].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.
diff --git a/net/mac80211/rc80211_minstrel.h b/net/mac80211/rc80211_minstrel.h
index 38158b0..713c81e 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;
diff --git a/net/mac80211/rc80211_minstrel_debugfs.c b/net/mac80211/rc80211_minstrel_debugfs.c
index 3ed69ef..0a60bac 100644
--- a/net/mac80211/rc80211_minstrel_debugfs.c
+++ b/net/mac80211/rc80211_minstrel_debugfs.c
@@ -85,10 +85,12 @@ minstrel_stats_open(struct inode *inode, struct file *file)
file->private_data = ms;
p = ms->buf;
p += sprintf(p, "\n");
- p += sprintf(p, "best __________rate_________ __statistics__ "
- "________last_______ ______sum-of________\n");
- p += sprintf(p, "rate [name idx airtime max_tp] [ ø(tp) ø(prob)] "
- "[prob.|retry|suc|att] [#success | #attempts]\n");
+ p += sprintf(p, "best __________rate_________ ______"
+ "statistics______ ________last_______ "
+ "______sum-of________\n");
+ p += sprintf(p, "rate [name idx airtime max_tp] [ ø(tp) ø(prob) "
+ "sd(prob)] [prob.|retry|suc|att] "
+ "[#success | #attempts]\n");
for (i = 0; i < mi->n_rates; i++) {
struct minstrel_rate *mr = &mi->r[i];
@@ -110,11 +112,13 @@ minstrel_stats_open(struct inode *inode, struct file *file)
prob = MINSTREL_TRUNC(mrs->cur_prob * 1000);
eprob = MINSTREL_TRUNC(mrs->prob_ewma * 1000);
- p += sprintf(p, "%4u.%1u %4u.%1u %3u.%1u %3u.%1u %3u"
- " %3u %-3u %9llu %-9llu\n",
+ p += sprintf(p, "%4u.%1u %4u.%1u %3u.%1u %3u.%1u"
+ " %3u.%1u %3u %3u %-3u "
+ "%9llu %-9llu\n",
tp_max / 10, tp_max % 10,
tp_avg / 10, tp_avg % 10,
eprob / 10, eprob % 10,
+ mrs->prob_ewmsd / 10, mrs->prob_ewmsd % 10,
prob / 10, prob % 10,
mrs->retry_count,
mrs->last_success,
@@ -180,11 +184,12 @@ minstrel_stats_csv_open(struct inode *inode, struct file *file)
prob = MINSTREL_TRUNC(mrs->cur_prob * 1000);
eprob = MINSTREL_TRUNC(mrs->prob_ewma * 1000);
- p += sprintf(p, "%u.%u,%u.%u,%u.%u,%u.%u,%u,%u,%u,"
+ p += sprintf(p, "%u.%u,%u.%u,%u.%u,%u.%u,%u.%u,%u,%u,%u,"
"%llu,%llu,%d,%d\n",
tp_max / 10, tp_max % 10,
tp_avg / 10, tp_avg % 10,
eprob / 10, eprob % 10,
+ mrs->prob_ewmsd / 10, mrs->prob_ewmsd % 10,
prob / 10, prob % 10,
mrs->retry_count,
mrs->last_success,
diff --git a/net/mac80211/rc80211_minstrel_ht_debugfs.c b/net/mac80211/rc80211_minstrel_ht_debugfs.c
index de034e4..e950059 100644
--- a/net/mac80211/rc80211_minstrel_ht_debugfs.c
+++ b/net/mac80211/rc80211_minstrel_ht_debugfs.c
@@ -86,11 +86,13 @@ minstrel_ht_stats_dump(struct minstrel_ht_sta *mi, int i, char *p)
prob = MINSTREL_TRUNC(mrs->cur_prob * 1000);
eprob = MINSTREL_TRUNC(mrs->prob_ewma * 1000);
- p += sprintf(p, "%4u.%1u %4u.%1u %3u.%1u %3u.%1u "
- "%3u %3u %-3u %9llu %-9llu\n",
+ p += sprintf(p, "%4u.%1u %4u.%1u %3u.%1u %3u.%1u"
+ " %3u.%1u %3u %3u %-3u "
+ "%9llu %-9llu\n",
tp_max / 10, tp_max % 10,
tp_avg / 10, tp_avg % 10,
eprob / 10, eprob % 10,
+ mrs->prob_ewmsd / 10, mrs->prob_ewmsd % 10,
prob / 10, prob % 10,
mrs->retry_count,
mrs->last_success,
@@ -128,10 +130,10 @@ minstrel_ht_stats_open(struct inode *inode, struct file *file)
p += sprintf(p, "\n");
p += sprintf(p, " best ____________rate__________ "
- "__statistics__ ________last_______ "
+ "______statistics______ ________last_______ "
"______sum-of________\n");
p += sprintf(p, "mode guard # rate [name idx airtime max_tp] "
- "[ ø(tp) ø(prob)] [prob.|retry|suc|att] [#success | "
+ "[ ø(tp) ø(prob) sd(prob)] [prob.|retry|suc|att] [#success | "
"#attempts]\n");
p = minstrel_ht_stats_dump(mi, MINSTREL_CCK_GROUP, p);
@@ -232,10 +234,12 @@ minstrel_ht_stats_csv_dump(struct minstrel_ht_sta *mi, int i, char *p,
prob = MINSTREL_TRUNC(mrs->cur_prob * 1000);
eprob = MINSTREL_TRUNC(mrs->prob_ewma * 1000);
- p += sprintf(p, "%u.%u,%u.%u,%u.%u,%u.%u,%u,%u,%u,%llu,%llu,",
+ p += sprintf(p, "%u.%u,%u.%u,%u.%u,%u.%u,%u.%u,%u,%u,"
+ "%u,%llu,%llu,",
tp_max / 10, tp_max % 10,
tp_avg / 10, tp_avg % 10,
eprob / 10, eprob % 10,
+ mrs->prob_ewmsd / 10, mrs->prob_ewmsd % 10,
prob / 10, prob % 10,
mrs->retry_count,
mrs->last_success,
--
2.3.0
--
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