mac80211: Dynamically set CoDel parameters per station

CoDel can be too aggressive if a station sends at a very low rate,
leading reduced throughput. This gets worse the more stations are
present, as each station gets more bursty the longer the round-robin
scheduling between stations takes.

This adds dynamic adjustment of CoDel parameters per station. It uses
the rate selection information to estimate throughput and sets more
lenient CoDel parameters if the estimated throughput is below a
threshold (modified by the number of active stations).

A new callback is added that drivers can use to notify mac80211 about
changes in expected throughput, so the same adjustment can be made for
cards that implement rate control in firmware. Drivers that don't use
this will just get the default parameters.

Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
[remove currently unnecessary EXPORT_SYMBOL, fix kernel-doc, remove
inline annotation]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index 5609cacb20d5..b58c3b19ab78 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -394,6 +394,14 @@ struct ieee80211_sta_rx_stats {
 };
 
 /**
+ * The bandwidth threshold below which the per-station CoDel parameters will be
+ * scaled to be more lenient (to prevent starvation of slow stations). This
+ * value will be scaled by the number of active stations when it is being
+ * applied.
+ */
+#define STA_SLOW_THRESHOLD 6000 /* 6 Mbps */
+
+/**
  * struct sta_info - STA information
  *
  * This structure collects information about a station that
@@ -446,6 +454,7 @@ struct ieee80211_sta_rx_stats {
  * @known_smps_mode: the smps_mode the client thinks we are in. Relevant for
  *	AP only.
  * @cipher_scheme: optional cipher scheme for this station
+ * @cparams: CoDel parameters for this station.
  * @reserved_tid: reserved TID (if any, otherwise IEEE80211_TID_UNRESERVED)
  * @fast_tx: TX fastpath information
  * @fast_rx: RX fastpath information
@@ -549,6 +558,8 @@ struct sta_info {
 	enum ieee80211_smps_mode known_smps_mode;
 	const struct ieee80211_cipher_scheme *cipher_scheme;
 
+	struct codel_params cparams;
+
 	u8 reserved_tid;
 
 	struct cfg80211_chan_def tdls_chandef;