ath9k: Introduce airtime fairness scheduling between stations

This reworks the ath9k driver to schedule transmissions to connected
stations in a way that enforces airtime fairness between them. It
accomplishes this by measuring the time spent transmitting to or
receiving from a station at TX and RX completion, and accounting this to
a per-station, per-QoS level airtime deficit. Then, an FQ-CoDel based
deficit scheduler is employed at packet dequeue time, to control which
station gets the next transmission opportunity.

Airtime fairness can significantly improve the efficiency of the network
when station rates vary. The following throughput values are from a
simple three-station test scenario, where two stations operate at the
highest HT20 rate, and one station at the lowest, and the scheduler is
employed at the access point:

                  Before   /   After
Fast station 1:    19.17   /   25.09 Mbps
Fast station 2:    19.83   /   25.21 Mbps
Slow station:       2.58   /    1.77 Mbps
Total:             41.58   /   52.07 Mbps

The benefit of airtime fairness goes up the more stations are present.
In a 30-station test with one station artificially limited to 1 Mbps,
we have seen aggregate throughput go from 2.14 to 17.76 Mbps.

Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/drivers/net/wireless/ath/ath9k/debug.h b/drivers/net/wireless/ath/ath9k/debug.h
index a078cdd3170d..249f8141cd00 100644
--- a/drivers/net/wireless/ath/ath9k/debug.h
+++ b/drivers/net/wireless/ath/ath9k/debug.h
@@ -221,6 +221,11 @@ struct ath_rx_rate_stats {
 	} cck_stats[4];
 };
 
+struct ath_airtime_stats {
+	u32 rx_airtime;
+	u32 tx_airtime;
+};
+
 #define ANT_MAIN 0
 #define ANT_ALT  1
 
@@ -314,12 +319,20 @@ ath9k_debug_sync_cause(struct ath_softc *sc, u32 sync_cause)
 void ath_debug_rate_stats(struct ath_softc *sc,
 			  struct ath_rx_status *rs,
 			  struct sk_buff *skb);
+void ath_debug_airtime(struct ath_softc *sc,
+		       struct ath_node *an,
+		       u32 rx, u32 tx);
 #else
 static inline void ath_debug_rate_stats(struct ath_softc *sc,
 					struct ath_rx_status *rs,
 					struct sk_buff *skb)
 {
 }
+static inline void ath_debug_airtime(struct ath_softc *sc,
+			      struct ath_node *an,
+			      u32 rx, u32 tx)
+{
+}
 #endif /* CONFIG_ATH9K_STATION_STATISTICS */
 
 #endif /* DEBUG_H */