minstrel: improve performance for non-MRR drivers

This patch enhances minstrel's performance for non-MRR setups,
by preventing it from sampling slower rates with >95% success
probability and by putting at least 1 non-sample frame between
several sample frames.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --git a/net/mac80211/rc80211_minstrel.c b/net/mac80211/rc80211_minstrel.c
index 759ddd8..c10debc 100644 (file)
--- a/net/mac80211/rc80211_minstrel.c
+++ b/net/mac80211/rc80211_minstrel.c
@@ -126,7 +126,9 @@ minstrel_update_stats(struct minstrel_priv *mp, struct minstrel_sta_info *mi)
                        mr->adjusted_retry_count = mr->retry_count >> 1;
                        if (mr->adjusted_retry_count > 2)
                                mr->adjusted_retry_count = 2;
+                       mr->sample_limit = 4;
                } else {
+                       mr->sample_limit = -1;
                        mr->adjusted_retry_count = mr->retry_count;
                }
                if (!mr->adjusted_retry_count)
@@ -265,7 +267,8 @@ minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
                        (mi->sample_count + mi->sample_deferred / 2);
 
        /* delta > 0: sampling required */
-       if (delta > 0) {
+       if ((delta > 0) && (mrr || !mi->prev_sample)) {
+               struct minstrel_rate *msr;
                if (mi->packet_count >= 10000) {
                        mi->sample_deferred = 0;
                        mi->sample_count = 0;
@@ -284,13 +287,20 @@ minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
                }
 
                sample_ndx = minstrel_get_next_sample(mi);
+               msr = &mi->r[sample_ndx];
                sample = true;
-               sample_slower = mrr && (mi->r[sample_ndx].perfect_tx_time >
+               sample_slower = mrr && (msr->perfect_tx_time >
                        mi->r[ndx].perfect_tx_time);
 
                if (!sample_slower) {
-                       ndx = sample_ndx;
-                       mi->sample_count++;
+                       if (msr->sample_limit != 0) {
+                               ndx = sample_ndx;
+                               mi->sample_count++;
+                               if (msr->sample_limit > 0)
+                                       msr->sample_limit--;
+                       } else {
+                               sample = false;
+                       }
                } else {
                        /* Only use IEEE80211_TX_CTL_RATE_CTRL_PROBE to mark
                         * packets that have the sampling rate deferred to the
@@ -302,10 +312,20 @@ minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
                        mi->sample_deferred++;
                }
        }
+       mi->prev_sample = sample;
+
+       /* If we're not using MRR and the sampling rate already
+        * has a probability of >95%, we shouldn't be attempting
+        * to use it, as this only wastes precious airtime */
+       if (!mrr && sample && (mi->r[ndx].probability > 17100))
+               ndx = mi->max_tp_rate;
+
        ar[0].idx = mi->r[ndx].rix;
        ar[0].count = minstrel_get_retry_count(&mi->r[ndx], info);
 
        if (!mrr) {
+               if (!sample)
+                       ar[0].count = mp->max_retry;
                ar[1].idx = mi->lowest_rix;
                ar[1].count = mp->max_retry;
                return;
@@ -401,6 +421,7 @@ minstrel_rate_init(void *priv, struct ieee80211_supported_band *sband,
 
                /* calculate maximum number of retransmissions before
                 * fallback (based on maximum segment size) */
+               mr->sample_limit = -1;
                mr->retry_count = 1;
                mr->retry_count_cts = 1;
                mr->retry_count_rtscts = 1;

diff --git a/net/mac80211/rc80211_minstrel.h b/net/mac80211/rc80211_minstrel.h
index 9a90a6a..869fe0e 100644 (file)
--- a/net/mac80211/rc80211_minstrel.h
+++ b/net/mac80211/rc80211_minstrel.h
@@ -16,6 +16,7 @@ struct minstrel_rate {
        unsigned int perfect_tx_time;
        unsigned int ack_time;
 
+       int sample_limit;
        unsigned int retry_count;
        unsigned int retry_count_cts;
        unsigned int retry_count_rtscts;
@@ -57,6 +58,7 @@ struct minstrel_sta_info {
 
        int n_rates;
        struct minstrel_rate *r;
+       bool prev_sample;
 
        /* sampling table */
        u8 *sample_table;