mac80211: improve minstrel_ht rate sorting by throughput & probability

This patch improves the way minstrel_ht sorts rates according to throughput
and success probability. 3 FOR-loops across the entire rate and mcs group set
in function minstrel_ht_update_stats() which where used to determine the
fastest, second fastest and most robust rate are reduced to 2 FOR-loop.

The sorted list of rates according throughput is extended to the best four
rates as we need them in upcoming joint rate and power control. The sorting
is done via the new function minstrel_ht_sort_best_tp_rates(). The annotation
of those 4 best throughput rates in the debugfs file rc-stats is changes to:
"A,B,C,D", where A is the fastest rate and C the 4th fastest.
Signed-off-by: Thomas Huehn <thomas@net.t-labs.tu-berlin.de>
Tested-by: Stefan Venz <ikstream86@gmail.com>
Acked-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/rc80211_minstrel_ht.h

@@ -33,10 +33,9 @@ struct minstrel_mcs_group_data {
 	/* bitfield of supported MCS rates of this group */
 	u8 supported;
 
-	/* selected primary rates */
-	unsigned int max_tp_rate;
-	unsigned int max_tp_rate2;
-	unsigned int max_prob_rate;
+	/* sorted rate set within a MCS group*/
+	u8 max_group_tp_rate[MAX_THR_RATES];
+	u8 max_group_prob_rate;
 
 	/* MCS rate statistics */
 	struct minstrel_rate_stats rates[MCS_GROUP_RATES];
@@ -52,15 +51,9 @@ struct minstrel_ht_sta {
 	/* ampdu length (EWMA) */
 	unsigned int avg_ampdu_len;
 
-	/* best throughput rate */
-	unsigned int max_tp_rate;
-
-	/* second best throughput rate */
-	unsigned int max_tp_rate2;
-
-	/* best probability rate */
-	unsigned int max_prob_rate;
-	unsigned int max_prob_streams;
+	/* overall sorted rate set */
+	u8 max_tp_rate[MAX_THR_RATES];
+	u8 max_prob_rate;
 
 	/* time of last status update */
 	unsigned long stats_update;

net/mac80211/rc80211_minstrel_ht_debugfs.c

@@ -46,8 +46,10 @@ minstrel_ht_stats_dump(struct minstrel_ht_sta *mi, int i, char *p)
 		else
 			p += sprintf(p, "HT%c0/%cGI ", htmode, gimode);
 
-		*(p++) = (idx == mi->max_tp_rate) ? 'T' : ' ';
-		*(p++) = (idx == mi->max_tp_rate2) ? 't' : ' ';
+		*(p++) = (idx == mi->max_tp_rate[0]) ? 'A' : ' ';
+		*(p++) = (idx == mi->max_tp_rate[1]) ? 'B' : ' ';
+		*(p++) = (idx == mi->max_tp_rate[2]) ? 'C' : ' ';
+		*(p++) = (idx == mi->max_tp_rate[3]) ? 'D' : ' ';
 		*(p++) = (idx == mi->max_prob_rate) ? 'P' : ' ';
 
 		if (i == max_mcs) {
@@ -100,8 +102,8 @@ minstrel_ht_stats_open(struct inode *inode, struct file *file)
 
 	file->private_data = ms;
 	p = ms->buf;
-	p += sprintf(p, "type         rate     throughput  ewma prob   this prob  "
-			"retry   this succ/attempt   success    attempts\n");
+	p += sprintf(p, "type           rate     throughput  ewma prob   "
+		     "this prob  retry   this succ/attempt   success    attempts\n");
 
 	p = minstrel_ht_stats_dump(mi, max_mcs, p);
 	for (i = 0; i < max_mcs; i++)