mac80211: mesh: use average bitrate for link metric calculation

Use bitrate moving average to smooth out link metric and stablize path
selection.
Signed-off-by: Julan Hsu <julanhsu@google.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/cfg.c

@@ -1231,6 +1231,11 @@ static void sta_apply_mesh_params(struct ieee80211_local *local,
 			ieee80211_mps_sta_status_update(sta);
 			changed |= ieee80211_mps_set_sta_local_pm(sta,
 				      sdata->u.mesh.mshcfg.power_mode);
+
+			ewma_mesh_tx_rate_avg_init(&sta->mesh->tx_rate_avg);
+			/* init at low value */
+			ewma_mesh_tx_rate_avg_add(&sta->mesh->tx_rate_avg, 10);
+
 			break;
 		case NL80211_PLINK_LISTEN:
 		case NL80211_PLINK_BLOCKED:

net/mac80211/mesh_hwmp.c

@@ -300,6 +300,7 @@ void ieee80211s_update_metric(struct ieee80211_local *local,
 {
 	struct ieee80211_tx_info *txinfo = st->info;
 	int failed;
+	struct rate_info rinfo;
 
 	failed = !(txinfo->flags & IEEE80211_TX_STAT_ACK);
 
@@ -310,12 +311,15 @@ void ieee80211s_update_metric(struct ieee80211_local *local,
 	if (ewma_mesh_fail_avg_read(&sta->mesh->fail_avg) >
 			LINK_FAIL_THRESH)
 		mesh_plink_broken(sta);
+
+	sta_set_rate_info_tx(sta, &sta->tx_stats.last_rate, &rinfo);
+	ewma_mesh_tx_rate_avg_add(&sta->mesh->tx_rate_avg,
+				  cfg80211_calculate_bitrate(&rinfo));
 }
 
 static u32 airtime_link_metric_get(struct ieee80211_local *local,
 				   struct sta_info *sta)
 {
-	struct rate_info rinfo;
 	/* This should be adjusted for each device */
 	int device_constant = 1 << ARITH_SHIFT;
 	int test_frame_len = TEST_FRAME_LEN << ARITH_SHIFT;
@@ -339,8 +343,7 @@ static u32 airtime_link_metric_get(struct ieee80211_local *local,
 		if (fail_avg > LINK_FAIL_THRESH)
 			return MAX_METRIC;
 
-		sta_set_rate_info_tx(sta, &sta->tx_stats.last_rate, &rinfo);
-		rate = cfg80211_calculate_bitrate(&rinfo);
+		rate = ewma_mesh_tx_rate_avg_read(&sta->mesh->tx_rate_avg);
 		if (WARN_ON(!rate))
 			return MAX_METRIC;
 

net/mac80211/sta_info.h

@@ -353,6 +353,7 @@ struct ieee80211_fast_rx {
 
 /* we use only values in the range 0-100, so pick a large precision */
 DECLARE_EWMA(mesh_fail_avg, 20, 8)
+DECLARE_EWMA(mesh_tx_rate_avg, 8, 16)
 
 /**
  * struct mesh_sta - mesh STA information
@@ -376,6 +377,7 @@ DECLARE_EWMA(mesh_fail_avg, 20, 8)
  *	processed
  * @connected_to_gate: true if mesh STA has a path to a mesh gate
  * @fail_avg: moving percentage of failed MSDUs
+ * @tx_rate_avg: moving average of tx bitrate
  */
 struct mesh_sta {
 	struct timer_list plink_timer;
@@ -404,6 +406,8 @@ struct mesh_sta {
 
 	/* moving percentage of failed MSDUs */
 	struct ewma_mesh_fail_avg fail_avg;
+	/* moving average of tx bitrate */
+	struct ewma_mesh_tx_rate_avg tx_rate_avg;
 };
 
 DECLARE_EWMA(signal, 10, 8)