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>

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 76ed24a201eb9075672e8d2f55fffe5ae147923d..e01daff1e2558187ce2872c29c777417271cbfdf 100644 (file)
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -4204,6 +4204,22 @@ void ieee80211_get_tx_rates(struct ieee80211_vif *vif,
                            struct ieee80211_tx_rate *dest,
                            int max_rates);
 
+/**
+ * ieee80211_sta_set_expected_throughput - set the expected tpt for a station
+ *
+ * Call this function to notify mac80211 about a change in expected throughput
+ * to a station. A driver for a device that does rate control in firmware can
+ * call this function when the expected throughput estimate towards a station
+ * changes. The information is used to tune the CoDel AQM applied to traffic
+ * going towards that station (which can otherwise be too aggressive and cause
+ * slow stations to starve).
+ *
+ * @pubsta: the station to set throughput for.
+ * @thr: the current expected throughput in kbps.
+ */
+void ieee80211_sta_set_expected_throughput(struct ieee80211_sta *pubsta,
+                                          u32 thr);
+
 /**
  * ieee80211_tx_status - transmit status callback
  *

diff --git a/net/mac80211/debugfs_sta.c b/net/mac80211/debugfs_sta.c
index 42601820db20e6c338f919dbc3c09481669d4f6e..b15412c21ac9355762a0b99ad99096d65a0a001b 100644 (file)
--- a/net/mac80211/debugfs_sta.c
+++ b/net/mac80211/debugfs_sta.c
@@ -152,6 +152,12 @@ static ssize_t sta_aqm_read(struct file *file, char __user *userbuf,
        spin_lock_bh(&local->fq.lock);
        rcu_read_lock();
 
+       p += scnprintf(p,
+                      bufsz+buf-p,
+                      "target %uus interval %uus ecn %s\n",
+                      codel_time_to_us(sta->cparams.target),
+                      codel_time_to_us(sta->cparams.interval),
+                      sta->cparams.ecn ? "yes" : "no");
        p += scnprintf(p,
                       bufsz+buf-p,
                       "tid ac backlog-bytes backlog-packets new-flows drops marks overlimit collisions tx-bytes tx-packets\n");

diff --git a/net/mac80211/rate.c b/net/mac80211/rate.c
index ea1f4315c521be976c822918d7d821cffd3cc0e9..76f303fda3edaf15a98b4d159a6b455e1e8fbfc5 100644 (file)
--- a/net/mac80211/rate.c
+++ b/net/mac80211/rate.c
@@ -943,6 +943,8 @@ int rate_control_set_rates(struct ieee80211_hw *hw,
 
        drv_sta_rate_tbl_update(hw_to_local(hw), sta->sdata, pubsta);
 
+       ieee80211_sta_set_expected_throughput(pubsta, sta_get_expected_throughput(sta));
+
        return 0;
 }
 EXPORT_SYMBOL(rate_control_set_rates);
@@ -991,4 +993,3 @@ void rate_control_deinitialize(struct ieee80211_local *local)
        local->rate_ctrl = NULL;
        rate_control_free(local, ref);
 }
-

diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index 7cdf7a835bb01e8fade3b9d9bb6efaa19158f72b..f59434ac385df7fa68eba438070ef335ef6c9d86 100644 (file)
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -20,6 +20,7 @@
 #include <linux/timer.h>
 #include <linux/rtnetlink.h>
 
+#include <net/codel.h>
 #include <net/mac80211.h>
 #include "ieee80211_i.h"
 #include "driver-ops.h"
@@ -425,6 +426,11 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
 
        sta->sta.max_rc_amsdu_len = IEEE80211_MAX_MPDU_LEN_HT_BA;
 
+       sta->cparams.ce_threshold = CODEL_DISABLED_THRESHOLD;
+       sta->cparams.target = MS2TIME(20);
+       sta->cparams.interval = MS2TIME(100);
+       sta->cparams.ecn = true;
+
        sta_dbg(sdata, "Allocated STA %pM\n", sta->sta.addr);
 
        return sta;
@@ -2310,3 +2316,27 @@ unsigned long ieee80211_sta_last_active(struct sta_info *sta)
                return stats->last_rx;
        return sta->status_stats.last_ack;
 }
+
+static void sta_update_codel_params(struct sta_info *sta, u32 thr)
+{
+       if (!sta->sdata->local->ops->wake_tx_queue)
+               return;
+
+       if (thr && thr < STA_SLOW_THRESHOLD * sta->local->num_sta) {
+               sta->cparams.target = MS2TIME(50);
+               sta->cparams.interval = MS2TIME(300);
+               sta->cparams.ecn = false;
+       } else {
+               sta->cparams.target = MS2TIME(20);
+               sta->cparams.interval = MS2TIME(100);
+               sta->cparams.ecn = true;
+       }
+}
+
+void ieee80211_sta_set_expected_throughput(struct ieee80211_sta *pubsta,
+                                          u32 thr)
+{
+       struct sta_info *sta = container_of(pubsta, struct sta_info, sta);
+
+       sta_update_codel_params(sta, thr);
+}

diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index 5609cacb20d5f31e02ba877f88a6f0290e18ce8b..b58c3b19ab78bbb6fd4e233e0addb49b9cc3163f 100644 (file)
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -393,6 +393,14 @@ struct ieee80211_sta_rx_stats {
        u64 msdu[IEEE80211_NUM_TIDS + 1];
 };
 
+/**
+ * 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
  *
@@ -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;

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 04b22f8982fe42b41364d8d7feee0d5bd036c64a..b8dc41191835de940da73e3c2c5cbfd768ab2516 100644 (file)
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -1340,9 +1340,16 @@ static struct sk_buff *fq_tin_dequeue_func(struct fq *fq,
 
        local = container_of(fq, struct ieee80211_local, fq);
        txqi = container_of(tin, struct txq_info, tin);
-       cparams = &local->cparams;
        cstats = &txqi->cstats;
 
+       if (txqi->txq.sta) {
+               struct sta_info *sta = container_of(txqi->txq.sta,
+                                                   struct sta_info, sta);
+               cparams = &sta->cparams;
+       } else {
+               cparams = &local->cparams;
+       }
+
        if (flow == &txqi->def_flow)
                cvars = &txqi->def_cvars;
        else