[PATCH 1/7] mac80211: switch airtime fairness back to deficit round-robin scheduling

[PATCH 1/7] mac80211: switch airtime fairness back to deficit round-robin scheduling

[Felix Fietkau]

This reverts commits 6a789ba679d652587532cec2a0e0274fda172f3b and
2433647bc8d983a543e7d31b41ca2de1c7e2c198.

The virtual time scheduler code has a number of issues:
- queues slowed down by hardware/firmware powersave handling were not properly
  handled.
- on ath10k in push-pull mode, tx queues that the driver tries to pull from
  were starved, causing excessive latency
- delay between tx enqueue and reported airtime use were causing excessively
  bursty tx behavior

The bursty behavior may also be present on the round-robin scheduler, but there
it is much easier to fix without introducing additional regressions

Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 include/net/mac80211.h        |  17 +-
 net/mac80211/cfg.c            |  35 +---
 net/mac80211/debugfs.c        |  70 ++-----
 net/mac80211/debugfs_netdev.c |  32 +--
 net/mac80211/debugfs_sta.c    |  24 +--
 net/mac80211/ieee80211_i.h    | 182 ++---------------
 net/mac80211/iface.c          |   4 -
 net/mac80211/main.c           |  11 +-
 net/mac80211/rx.c             |   6 +-
 net/mac80211/sta_info.c       |  67 ++-----
 net/mac80211/sta_info.h       |  11 +-
 net/mac80211/status.c         |  19 --
 net/mac80211/tx.c             | 366 ++++++++++------------------------
 13 files changed, 193 insertions(+), 651 deletions(-)

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 27f24ac0426d..48d167c5a726 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -6832,6 +6832,9 @@ static inline void ieee80211_txq_schedule_end(struct ieee80211_hw *hw, u8 ac)
 {
 }
 
+void __ieee80211_schedule_txq(struct ieee80211_hw *hw,
+			      struct ieee80211_txq *txq, bool force);
+
 /**
  * ieee80211_schedule_txq - schedule a TXQ for transmission
  *
@@ -6844,7 +6847,11 @@ static inline void ieee80211_txq_schedule_end(struct ieee80211_hw *hw, u8 ac)
  * The driver may call this function if it has buffered packets for
  * this TXQ internally.
  */
-void ieee80211_schedule_txq(struct ieee80211_hw *hw, struct ieee80211_txq *txq);
+static inline void
+ieee80211_schedule_txq(struct ieee80211_hw *hw, struct ieee80211_txq *txq)
+{
+	__ieee80211_schedule_txq(hw, txq, true);
+}
 
 /**
  * ieee80211_return_txq - return a TXQ previously acquired by ieee80211_next_txq()
@@ -6856,8 +6863,12 @@ void ieee80211_schedule_txq(struct ieee80211_hw *hw, struct ieee80211_txq *txq);
  * The driver may set force=true if it has buffered packets for this TXQ
  * internally.
  */
-void ieee80211_return_txq(struct ieee80211_hw *hw, struct ieee80211_txq *txq,
-			  bool force);
+static inline void
+ieee80211_return_txq(struct ieee80211_hw *hw, struct ieee80211_txq *txq,
+		     bool force)
+{
+	__ieee80211_schedule_txq(hw, txq, force);
+}
 
 /**
  * ieee80211_txq_may_transmit - check whether TXQ is allowed to transmit
diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index b387f5f4fef0..fd6c4291c971 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -1581,38 +1581,6 @@ static void sta_apply_mesh_params(struct ieee80211_local *local,
 #endif
 }
 
-static void sta_apply_airtime_params(struct ieee80211_local *local,
-				     struct sta_info *sta,
-				     struct station_parameters *params)
-{
-	u8 ac;
-
-	for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
-		struct airtime_sched_info *air_sched = &local->airtime[ac];
-		struct airtime_info *air_info = &sta->airtime[ac];
-		struct txq_info *txqi;
-		u8 tid;
-
-		spin_lock_bh(&air_sched->lock);
-		for (tid = 0; tid < IEEE80211_NUM_TIDS + 1; tid++) {
-			if (air_info->weight == params->airtime_weight ||
-			    !sta->sta.txq[tid] ||
-			    ac != ieee80211_ac_from_tid(tid))
-				continue;
-
-			airtime_weight_set(air_info, params->airtime_weight);
-
-			txqi = to_txq_info(sta->sta.txq[tid]);
-			if (RB_EMPTY_NODE(&txqi->schedule_order))
-				continue;
-
-			ieee80211_update_airtime_weight(local, air_sched,
-							0, true);
-		}
-		spin_unlock_bh(&air_sched->lock);
-	}
-}
-
 static int sta_apply_parameters(struct ieee80211_local *local,
 				struct sta_info *sta,
 				struct station_parameters *params)
@@ -1811,8 +1779,7 @@ static int sta_apply_parameters(struct ieee80211_local *local,
 		sta_apply_mesh_params(local, sta, params);
 
 	if (params->airtime_weight)
-		sta_apply_airtime_params(local, sta, params);
-
+		sta->airtime_weight = params->airtime_weight;
 
 	/* set the STA state after all sta info from usermode has been set */
 	if (test_sta_flag(sta, WLAN_STA_TDLS_PEER) ||
diff --git a/net/mac80211/debugfs.c b/net/mac80211/debugfs.c
index 1fe43b264d75..0c748b1eb023 100644
--- a/net/mac80211/debugfs.c
+++ b/net/mac80211/debugfs.c
@@ -216,14 +216,14 @@ static ssize_t aql_txq_limit_read(struct file *file,
 			"VI	%u		%u\n"
 			"BE	%u		%u\n"
 			"BK	%u		%u\n",
-			local->airtime[IEEE80211_AC_VO].aql_txq_limit_low,
-			local->airtime[IEEE80211_AC_VO].aql_txq_limit_high,
-			local->airtime[IEEE80211_AC_VI].aql_txq_limit_low,
-			local->airtime[IEEE80211_AC_VI].aql_txq_limit_high,
-			local->airtime[IEEE80211_AC_BE].aql_txq_limit_low,
-			local->airtime[IEEE80211_AC_BE].aql_txq_limit_high,
-			local->airtime[IEEE80211_AC_BK].aql_txq_limit_low,
-			local->airtime[IEEE80211_AC_BK].aql_txq_limit_high);
+			local->aql_txq_limit_low[IEEE80211_AC_VO],
+			local->aql_txq_limit_high[IEEE80211_AC_VO],
+			local->aql_txq_limit_low[IEEE80211_AC_VI],
+			local->aql_txq_limit_high[IEEE80211_AC_VI],
+			local->aql_txq_limit_low[IEEE80211_AC_BE],
+			local->aql_txq_limit_high[IEEE80211_AC_BE],
+			local->aql_txq_limit_low[IEEE80211_AC_BK],
+			local->aql_txq_limit_high[IEEE80211_AC_BK]);
 	return simple_read_from_buffer(user_buf, count, ppos,
 				       buf, len);
 }
@@ -255,11 +255,11 @@ static ssize_t aql_txq_limit_write(struct file *file,
 	if (ac >= IEEE80211_NUM_ACS)
 		return -EINVAL;
 
-	q_limit_low_old = local->airtime[ac].aql_txq_limit_low;
-	q_limit_high_old = local->airtime[ac].aql_txq_limit_high;
+	q_limit_low_old = local->aql_txq_limit_low[ac];
+	q_limit_high_old = local->aql_txq_limit_high[ac];
 
-	local->airtime[ac].aql_txq_limit_low = q_limit_low;
-	local->airtime[ac].aql_txq_limit_high = q_limit_high;
+	local->aql_txq_limit_low[ac] = q_limit_low;
+	local->aql_txq_limit_high[ac] = q_limit_high;
 
 	mutex_lock(&local->sta_mtx);
 	list_for_each_entry(sta, &local->sta_list, list) {
@@ -382,46 +382,6 @@ static const struct file_operations force_tx_status_ops = {
 	.llseek = default_llseek,
 };
 
-static ssize_t airtime_read(struct file *file,
-			    char __user *user_buf,
-			    size_t count,
-			    loff_t *ppos)
-{
-	struct ieee80211_local *local = file->private_data;
-	char buf[200];
-	u64 v_t[IEEE80211_NUM_ACS];
-	u64 wt[IEEE80211_NUM_ACS];
-	int len = 0, ac;
-
-	for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
-		spin_lock_bh(&local->airtime[ac].lock);
-		v_t[ac] = local->airtime[ac].v_t;
-		wt[ac] = local->airtime[ac].weight_sum;
-		spin_unlock_bh(&local->airtime[ac].lock);
-	}
-	len = scnprintf(buf, sizeof(buf),
-			"\tVO         VI         BE         BK\n"
-			"Virt-t\t%-10llu %-10llu %-10llu %-10llu\n"
-			"Weight\t%-10llu %-10llu %-10llu %-10llu\n",
-			v_t[0],
-			v_t[1],
-			v_t[2],
-			v_t[3],
-			wt[0],
-			wt[1],
-			wt[2],
-			wt[3]);
-
-	return simple_read_from_buffer(user_buf, count, ppos,
-				       buf, len);
-}
-
-static const struct file_operations airtime_ops = {
-	.read = airtime_read,
-	.open = simple_open,
-	.llseek = default_llseek,
-};
-
 #ifdef CONFIG_PM
 static ssize_t reset_write(struct file *file, const char __user *user_buf,
 			   size_t count, loff_t *ppos)
@@ -675,11 +635,7 @@ void debugfs_hw_add(struct ieee80211_local *local)
 	if (local->ops->wake_tx_queue)
 		DEBUGFS_ADD_MODE(aqm, 0600);
 
-	if (wiphy_ext_feature_isset(local->hw.wiphy,
-				    NL80211_EXT_FEATURE_AIRTIME_FAIRNESS)) {
-		DEBUGFS_ADD_MODE(airtime, 0600);
-		DEBUGFS_ADD_MODE(airtime_flags, 0600);
-	}
+	DEBUGFS_ADD_MODE(airtime_flags, 0600);
 
 	DEBUGFS_ADD(aql_txq_limit);
 	debugfs_create_u32("aql_threshold", 0600,
diff --git a/net/mac80211/debugfs_netdev.c b/net/mac80211/debugfs_netdev.c
index dfb194e15018..ead917501d6c 100644
--- a/net/mac80211/debugfs_netdev.c
+++ b/net/mac80211/debugfs_netdev.c
@@ -510,34 +510,6 @@ static ssize_t ieee80211_if_fmt_aqm(
 }
 IEEE80211_IF_FILE_R(aqm);
 
-static ssize_t ieee80211_if_fmt_airtime(
-	const struct ieee80211_sub_if_data *sdata, char *buf, int buflen)
-{
-	struct ieee80211_local *local = sdata->local;
-	struct ieee80211_txq *txq = sdata->vif.txq;
-	struct airtime_info *air_info;
-	int len;
-
-	if (!txq)
-		return 0;
-
-	spin_lock_bh(&local->airtime[txq->ac].lock);
-	air_info = to_airtime_info(txq);
-	len = scnprintf(buf,
-			buflen,
-			"RX: %llu us\nTX: %llu us\nWeight: %u\n"
-			"Virt-T: %lld us\n",
-			air_info->rx_airtime,
-			air_info->tx_airtime,
-			air_info->weight,
-			air_info->v_t);
-	spin_unlock_bh(&local->airtime[txq->ac].lock);
-
-	return len;
-}
-
-IEEE80211_IF_FILE_R(airtime);
-
 IEEE80211_IF_FILE(multicast_to_unicast, u.ap.multicast_to_unicast, HEX);
 
 /* IBSS attributes */
@@ -683,10 +655,8 @@ static void add_common_files(struct ieee80211_sub_if_data *sdata)
 
 	if (sdata->local->ops->wake_tx_queue &&
 	    sdata->vif.type != NL80211_IFTYPE_P2P_DEVICE &&
-	    sdata->vif.type != NL80211_IFTYPE_NAN) {
+	    sdata->vif.type != NL80211_IFTYPE_NAN)
 		DEBUGFS_ADD(aqm);
-		DEBUGFS_ADD(airtime);
-	}
 }
 
 static void add_sta_files(struct ieee80211_sub_if_data *sdata)
diff --git a/net/mac80211/debugfs_sta.c b/net/mac80211/debugfs_sta.c
index 182094be9001..1dc238fc24f0 100644
--- a/net/mac80211/debugfs_sta.c
+++ b/net/mac80211/debugfs_sta.c
@@ -202,7 +202,7 @@ static ssize_t sta_airtime_read(struct file *file, char __user *userbuf,
 	size_t bufsz = 400;
 	char *buf = kzalloc(bufsz, GFP_KERNEL), *p = buf;
 	u64 rx_airtime = 0, tx_airtime = 0;
-	u64 v_t[IEEE80211_NUM_ACS];
+	s64 deficit[IEEE80211_NUM_ACS];
 	ssize_t rv;
 	int ac;
 
@@ -210,18 +210,18 @@ static ssize_t sta_airtime_read(struct file *file, char __user *userbuf,
 		return -ENOMEM;
 
 	for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
-		spin_lock_bh(&local->airtime[ac].lock);
+		spin_lock_bh(&local->active_txq_lock[ac]);
 		rx_airtime += sta->airtime[ac].rx_airtime;
 		tx_airtime += sta->airtime[ac].tx_airtime;
-		v_t[ac] = sta->airtime[ac].v_t;
-		spin_unlock_bh(&local->airtime[ac].lock);
+		deficit[ac] = sta->airtime[ac].deficit;
+		spin_unlock_bh(&local->active_txq_lock[ac]);
 	}
 
 	p += scnprintf(p, bufsz + buf - p,
 		"RX: %llu us\nTX: %llu us\nWeight: %u\n"
-		"Virt-T: VO: %lld us VI: %lld us BE: %lld us BK: %lld us\n",
-		rx_airtime, tx_airtime, sta->airtime[0].weight,
-		v_t[0], v_t[1], v_t[2], v_t[3]);
+		"Deficit: VO: %lld us VI: %lld us BE: %lld us BK: %lld us\n",
+		rx_airtime, tx_airtime, sta->airtime_weight,
+		deficit[0], deficit[1], deficit[2], deficit[3]);
 
 	rv = simple_read_from_buffer(userbuf, count, ppos, buf, p - buf);
 	kfree(buf);
@@ -236,11 +236,11 @@ static ssize_t sta_airtime_write(struct file *file, const char __user *userbuf,
 	int ac;
 
 	for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
-		spin_lock_bh(&local->airtime[ac].lock);
+		spin_lock_bh(&local->active_txq_lock[ac]);
 		sta->airtime[ac].rx_airtime = 0;
 		sta->airtime[ac].tx_airtime = 0;
-		sta->airtime[ac].v_t = 0;
-		spin_unlock_bh(&local->airtime[ac].lock);
+		sta->airtime[ac].deficit = sta->airtime_weight;
+		spin_unlock_bh(&local->active_txq_lock[ac]);
 	}
 
 	return count;
@@ -263,10 +263,10 @@ static ssize_t sta_aql_read(struct file *file, char __user *userbuf,
 		return -ENOMEM;
 
 	for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
-		spin_lock_bh(&local->airtime[ac].lock);
+		spin_lock_bh(&local->active_txq_lock[ac]);
 		q_limit_l[ac] = sta->airtime[ac].aql_limit_low;
 		q_limit_h[ac] = sta->airtime[ac].aql_limit_high;
-		spin_unlock_bh(&local->airtime[ac].lock);
+		spin_unlock_bh(&local->active_txq_lock[ac]);
 		q_depth[ac] = atomic_read(&sta->airtime[ac].aql_tx_pending);
 	}
 
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 2190d08f4e34..8ef27e0f9371 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -818,16 +818,20 @@ enum txq_info_flags {
  * @def_flow: used as a fallback flow when a packet destined to @tin hashes to
  *	a fq_flow which is already owned by a different tin
  * @def_cvars: codel vars for @def_flow
- * @schedule_order: used with ieee80211_local->active_txqs
  * @frags: used to keep fragments created after dequeue
+ * @schedule_order: used with ieee80211_local->active_txqs
+ * @schedule_round: counter to prevent infinite loops on TXQ scheduling
  */
 struct txq_info {
 	struct fq_tin tin;
 	struct codel_vars def_cvars;
 	struct codel_stats cstats;
-	struct rb_node schedule_order;
+
+	u16 schedule_round;
+	struct list_head schedule_order;
 
 	struct sk_buff_head frags;
+
 	unsigned long flags;
 
 	/* keep last! */
@@ -923,8 +927,6 @@ struct ieee80211_link_data {
 	struct ieee80211_key __rcu *default_mgmt_key;
 	struct ieee80211_key __rcu *default_beacon_key;
 
-	struct airtime_info airtime[IEEE80211_NUM_ACS];
-
 	struct work_struct csa_finalize_work;
 	bool csa_block_tx; /* write-protected by sdata_lock and local->mtx */
 	struct cfg80211_chan_def csa_chandef;
@@ -1208,44 +1210,6 @@ enum mac80211_scan_state {
 	SCAN_ABORT,
 };
 
-/**
- * struct airtime_sched_info - state used for airtime scheduling and AQL
- *
- * @lock: spinlock that protects all the fields in this struct
- * @active_txqs: rbtree of currently backlogged queues, sorted by virtual time
- * @schedule_pos: the current position maintained while a driver walks the tree
- *                with ieee80211_next_txq()
- * @active_list: list of struct airtime_info structs that were active within
- *               the last AIRTIME_ACTIVE_DURATION (100 ms), used to compute
- *               weight_sum
- * @last_weight_update: used for rate limiting walking active_list
- * @last_schedule_time: tracks the last time a transmission was scheduled; used
- *                      for catching up v_t if no stations are eligible for
- *                      transmission.
- * @v_t: global virtual time; queues with v_t < this are eligible for
- *       transmission
- * @weight_sum: total sum of all active stations used for dividing airtime
- * @weight_sum_reciprocal: reciprocal of weight_sum (to avoid divisions in fast
- *                         path - see comment above
- *                         IEEE80211_RECIPROCAL_DIVISOR_64)
- * @aql_txq_limit_low: AQL limit when total outstanding airtime
- *                     is < IEEE80211_AQL_THRESHOLD
- * @aql_txq_limit_high: AQL limit when total outstanding airtime
- *                      is > IEEE80211_AQL_THRESHOLD
- */
-struct airtime_sched_info {
-	spinlock_t lock;
-	struct rb_root_cached active_txqs;
-	struct rb_node *schedule_pos;
-	struct list_head active_list;
-	u64 last_weight_update;
-	u64 last_schedule_activity;
-	u64 v_t;
-	u64 weight_sum;
-	u64 weight_sum_reciprocal;
-	u32 aql_txq_limit_low;
-	u32 aql_txq_limit_high;
-};
 DECLARE_STATIC_KEY_FALSE(aql_disable);
 
 struct ieee80211_local {
@@ -1259,8 +1223,13 @@ struct ieee80211_local {
 	struct codel_params cparams;
 
 	/* protects active_txqs and txqi->schedule_order */
-	struct airtime_sched_info airtime[IEEE80211_NUM_ACS];
+	spinlock_t active_txq_lock[IEEE80211_NUM_ACS];
+	struct list_head active_txqs[IEEE80211_NUM_ACS];
+	u16 schedule_round[IEEE80211_NUM_ACS];
+
 	u16 airtime_flags;
+	u32 aql_txq_limit_low[IEEE80211_NUM_ACS];
+	u32 aql_txq_limit_high[IEEE80211_NUM_ACS];
 	u32 aql_threshold;
 	atomic_t aql_total_pending_airtime;
 
@@ -1683,123 +1652,10 @@ static inline bool txq_has_queue(struct ieee80211_txq *txq)
 	return !(skb_queue_empty(&txqi->frags) && !txqi->tin.backlog_packets);
 }
 
-static inline struct airtime_info *to_airtime_info(struct ieee80211_txq *txq)
-{
-	struct ieee80211_sub_if_data *sdata;
-	struct sta_info *sta;
-
-	if (txq->sta) {
-		sta = container_of(txq->sta, struct sta_info, sta);
-		return &sta->airtime[txq->ac];
-	}
-
-	sdata = vif_to_sdata(txq->vif);
-	return &sdata->deflink.airtime[txq->ac];
-}
-
-/* To avoid divisions in the fast path, we keep pre-computed reciprocals for
- * airtime weight calculations. There are two different weights to keep track
- * of: The per-station weight and the sum of weights per phy.
- *
- * For the per-station weights (kept in airtime_info below), we use 32-bit
- * reciprocals with a devisor of 2^19. This lets us keep the multiplications and
- * divisions for the station weights as 32-bit operations at the cost of a bit
- * of rounding error for high weights; but the choice of divisor keeps rounding
- * errors <10% for weights <2^15, assuming no more than 8ms of airtime is
- * reported at a time.
- *
- * For the per-phy sum of weights the values can get higher, so we use 64-bit
- * operations for those with a 32-bit divisor, which should avoid any
- * significant rounding errors.
- */
-#define IEEE80211_RECIPROCAL_DIVISOR_64 0x100000000ULL
-#define IEEE80211_RECIPROCAL_SHIFT_64 32
-#define IEEE80211_RECIPROCAL_DIVISOR_32 0x80000U
-#define IEEE80211_RECIPROCAL_SHIFT_32 19
-
-static inline void airtime_weight_set(struct airtime_info *air_info, u16 weight)
-{
-	if (air_info->weight == weight)
-		return;
-
-	air_info->weight = weight;
-	if (weight) {
-		air_info->weight_reciprocal =
-			IEEE80211_RECIPROCAL_DIVISOR_32 / weight;
-	} else {
-		air_info->weight_reciprocal = 0;
-	}
-}
-
-static inline void airtime_weight_sum_set(struct airtime_sched_info *air_sched,
-					  int weight_sum)
-{
-	if (air_sched->weight_sum == weight_sum)
-		return;
-
-	air_sched->weight_sum = weight_sum;
-	if (air_sched->weight_sum) {
-		air_sched->weight_sum_reciprocal = IEEE80211_RECIPROCAL_DIVISOR_64;
-		do_div(air_sched->weight_sum_reciprocal, air_sched->weight_sum);
-	} else {
-		air_sched->weight_sum_reciprocal = 0;
-	}
-}
-
-/* A problem when trying to enforce airtime fairness is that we want to divide
- * the airtime between the currently *active* stations. However, basing this on
- * the instantaneous queue state of stations doesn't work, as queues tend to
- * oscillate very quickly between empty and occupied, leading to the scheduler
- * thinking only a single station is active when deciding whether to allow
- * transmission (and thus not throttling correctly).
- *
- * To fix this we use a timer-based notion of activity: a station is considered
- * active if it has been scheduled within the last 100 ms; we keep a separate
- * list of all the stations considered active in this manner, and lazily update
- * the total weight of active stations from this list (filtering the stations in
- * the list by their 'last active' time).
- *
- * We add one additional safeguard to guard against stations that manage to get
- * scheduled every 100 ms but don't transmit a lot of data, and thus don't use
- * up any airtime. Such stations would be able to get priority for an extended
- * period of time if they do start transmitting at full capacity again, and so
- * we add an explicit maximum for how far behind a station is allowed to fall in
- * the virtual airtime domain. This limit is set to a relatively high value of
- * 20 ms because the main mechanism for catching up idle stations is the active
- * state as described above; i.e., the hard limit should only be hit in
- * pathological cases.
- */
-#define AIRTIME_ACTIVE_DURATION (100 * NSEC_PER_MSEC)
-#define AIRTIME_MAX_BEHIND 20000 /* 20 ms */
-
-static inline bool airtime_is_active(struct airtime_info *air_info, u64 now)
-{
-	return air_info->last_scheduled >= now - AIRTIME_ACTIVE_DURATION;
-}
-
-static inline void airtime_set_active(struct airtime_sched_info *air_sched,
-				      struct airtime_info *air_info, u64 now)
-{
-	air_info->last_scheduled = now;
-	air_sched->last_schedule_activity = now;
-	list_move_tail(&air_info->list, &air_sched->active_list);
-}
-
-static inline bool airtime_catchup_v_t(struct airtime_sched_info *air_sched,
-				       u64 v_t, u64 now)
-{
-	air_sched->v_t = v_t;
-	return true;
-}
-
-static inline void init_airtime_info(struct airtime_info *air_info,
-				     struct airtime_sched_info *air_sched)
+static inline int ieee80211_bssid_match(const u8 *raddr, const u8 *addr)
 {
-	atomic_set(&air_info->aql_tx_pending, 0);
-	air_info->aql_limit_low = air_sched->aql_txq_limit_low;
-	air_info->aql_limit_high = air_sched->aql_txq_limit_high;
-	airtime_weight_set(air_info, IEEE80211_DEFAULT_AIRTIME_WEIGHT);
-	INIT_LIST_HEAD(&air_info->list);
+	return ether_addr_equal(raddr, addr) ||
+	       is_broadcast_ether_addr(raddr);
 }
 
 static inline bool
@@ -2047,14 +1903,6 @@ int ieee80211_tx_control_port(struct wiphy *wiphy, struct net_device *dev,
 			      u64 *cookie);
 int ieee80211_probe_mesh_link(struct wiphy *wiphy, struct net_device *dev,
 			      const u8 *buf, size_t len);
-void ieee80211_resort_txq(struct ieee80211_hw *hw,
-			  struct ieee80211_txq *txq);
-void ieee80211_unschedule_txq(struct ieee80211_hw *hw,
-			      struct ieee80211_txq *txq,
-			      bool purge);
-void ieee80211_update_airtime_weight(struct ieee80211_local *local,
-				     struct airtime_sched_info *air_sched,
-				     u64 now, bool force);
 
 /* HT */
 void ieee80211_apply_htcap_overrides(struct ieee80211_sub_if_data *sdata,
diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index 0cf5a395d925..56dd831fe45f 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -2176,10 +2176,6 @@ int ieee80211_if_add(struct ieee80211_local *local, const char *name,
 		}
 	}
 
-	for (i = 0; i < IEEE80211_NUM_ACS; i++)
-		init_airtime_info(&sdata->deflink.airtime[i],
-				  &local->airtime[i]);
-
 	ieee80211_set_default_queues(sdata);
 
 	sdata->deflink.ap_power_level = IEEE80211_UNSET_POWER_LEVEL;
diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index 08f153b82a23..e6c1cafbe9e5 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -784,13 +784,10 @@ struct ieee80211_hw *ieee80211_alloc_hw_nm(size_t priv_data_len,
 	spin_lock_init(&local->queue_stop_reason_lock);
 
 	for (i = 0; i < IEEE80211_NUM_ACS; i++) {
-		struct airtime_sched_info *air_sched = &local->airtime[i];
-
-		air_sched->active_txqs = RB_ROOT_CACHED;
-		INIT_LIST_HEAD(&air_sched->active_list);
-		spin_lock_init(&air_sched->lock);
-		air_sched->aql_txq_limit_low = IEEE80211_DEFAULT_AQL_TXQ_LIMIT_L;
-		air_sched->aql_txq_limit_high =
+		INIT_LIST_HEAD(&local->active_txqs[i]);
+		spin_lock_init(&local->active_txq_lock[i]);
+		local->aql_txq_limit_low[i] = IEEE80211_DEFAULT_AQL_TXQ_LIMIT_L;
+		local->aql_txq_limit_high[i] =
 			IEEE80211_DEFAULT_AQL_TXQ_LIMIT_H;
 	}
 
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index d017ad14d7db..834d2171f344 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -1565,8 +1565,12 @@ static void sta_ps_start(struct sta_info *sta)
 
 	for (tid = 0; tid < IEEE80211_NUM_TIDS; tid++) {
 		struct ieee80211_txq *txq = sta->sta.txq[tid];
+		struct txq_info *txqi = to_txq_info(txq);
 
-		ieee80211_unschedule_txq(&local->hw, txq, false);
+		spin_lock(&local->active_txq_lock[txq->ac]);
+		if (!list_empty(&txqi->schedule_order))
+			list_del_init(&txqi->schedule_order);
+		spin_unlock(&local->active_txq_lock[txq->ac]);
 
 		if (txq_has_queue(txq))
 			set_bit(tid, &sta->txq_buffered_tids);
diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index 014032369994..a1a2118b4bf0 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -559,11 +559,15 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
 	if (sta_prepare_rate_control(local, sta, gfp))
 		goto free_txq;
 
+	sta->airtime_weight = IEEE80211_DEFAULT_AIRTIME_WEIGHT;
 
 	for (i = 0; i < IEEE80211_NUM_ACS; i++) {
 		skb_queue_head_init(&sta->ps_tx_buf[i]);
 		skb_queue_head_init(&sta->tx_filtered[i]);
-		init_airtime_info(&sta->airtime[i], &local->airtime[i]);
+		sta->airtime[i].deficit = sta->airtime_weight;
+		atomic_set(&sta->airtime[i].aql_tx_pending, 0);
+		sta->airtime[i].aql_limit_low = local->aql_txq_limit_low[i];
+		sta->airtime[i].aql_limit_high = local->aql_txq_limit_high[i];
 	}
 
 	for (i = 0; i < IEEE80211_NUM_TIDS; i++)
@@ -2035,59 +2039,24 @@ void ieee80211_sta_set_buffered(struct ieee80211_sta *pubsta,
 }
 EXPORT_SYMBOL(ieee80211_sta_set_buffered);
 
-void ieee80211_register_airtime(struct ieee80211_txq *txq,
-				u32 tx_airtime, u32 rx_airtime)
+void ieee80211_sta_register_airtime(struct ieee80211_sta *pubsta, u8 tid,
+				    u32 tx_airtime, u32 rx_airtime)
 {
-	struct ieee80211_sub_if_data *sdata = vif_to_sdata(txq->vif);
-	struct ieee80211_local *local = sdata->local;
-	u64 weight_sum, weight_sum_reciprocal;
-	struct airtime_sched_info *air_sched;
-	struct airtime_info *air_info;
+	struct sta_info *sta = container_of(pubsta, struct sta_info, sta);
+	struct ieee80211_local *local = sta->sdata->local;
+	u8 ac = ieee80211_ac_from_tid(tid);
 	u32 airtime = 0;
 
-	air_sched = &local->airtime[txq->ac];
-	air_info = to_airtime_info(txq);
-
-	if (local->airtime_flags & AIRTIME_USE_TX)
+	if (sta->local->airtime_flags & AIRTIME_USE_TX)
 		airtime += tx_airtime;
-	if (local->airtime_flags & AIRTIME_USE_RX)
+	if (sta->local->airtime_flags & AIRTIME_USE_RX)
 		airtime += rx_airtime;
 
-	/* Weights scale so the unit weight is 256 */
-	airtime <<= 8;
-
-	spin_lock_bh(&air_sched->lock);
-
-	air_info->tx_airtime += tx_airtime;
-	air_info->rx_airtime += rx_airtime;
-
-	if (air_sched->weight_sum) {
-		weight_sum = air_sched->weight_sum;
-		weight_sum_reciprocal = air_sched->weight_sum_reciprocal;
-	} else {
-		weight_sum = air_info->weight;
-		weight_sum_reciprocal = air_info->weight_reciprocal;
-	}
-
-	/* Round the calculation of global vt */
-	air_sched->v_t += (u64)((airtime + (weight_sum >> 1)) *
-				weight_sum_reciprocal) >> IEEE80211_RECIPROCAL_SHIFT_64;
-	air_info->v_t += (u32)((airtime + (air_info->weight >> 1)) *
-			       air_info->weight_reciprocal) >> IEEE80211_RECIPROCAL_SHIFT_32;
-	ieee80211_resort_txq(&local->hw, txq);
-
-	spin_unlock_bh(&air_sched->lock);
-}
-
-void ieee80211_sta_register_airtime(struct ieee80211_sta *pubsta, u8 tid,
-				    u32 tx_airtime, u32 rx_airtime)
-{
-	struct ieee80211_txq *txq = pubsta->txq[tid];
-
-	if (!txq)
-		return;
-
-	ieee80211_register_airtime(txq, tx_airtime, rx_airtime);
+	spin_lock_bh(&local->active_txq_lock[ac]);
+	sta->airtime[ac].tx_airtime += tx_airtime;
+	sta->airtime[ac].rx_airtime += rx_airtime;
+	sta->airtime[ac].deficit -= airtime;
+	spin_unlock_bh(&local->active_txq_lock[ac]);
 }
 EXPORT_SYMBOL(ieee80211_sta_register_airtime);
 
@@ -2501,7 +2470,7 @@ void sta_set_sinfo(struct sta_info *sta, struct station_info *sinfo,
 	}
 
 	if (!(sinfo->filled & BIT_ULL(NL80211_STA_INFO_AIRTIME_WEIGHT))) {
-		sinfo->airtime_weight = sta->airtime[0].weight;
+		sinfo->airtime_weight = sta->airtime_weight;
 		sinfo->filled |= BIT_ULL(NL80211_STA_INFO_AIRTIME_WEIGHT);
 	}
 
diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index 218430790660..4ba0c252da95 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -135,25 +135,18 @@ enum ieee80211_agg_stop_reason {
 #define AIRTIME_USE_TX		BIT(0)
 #define AIRTIME_USE_RX		BIT(1)
 
-
 struct airtime_info {
 	u64 rx_airtime;
 	u64 tx_airtime;
-	u64 v_t;
-	u64 last_scheduled;
-	struct list_head list;
+	s64 deficit;
 	atomic_t aql_tx_pending; /* Estimated airtime for frames pending */
 	u32 aql_limit_low;
 	u32 aql_limit_high;
-	u32 weight_reciprocal;
-	u16 weight;
 };
 
 void ieee80211_sta_update_pending_airtime(struct ieee80211_local *local,
 					  struct sta_info *sta, u8 ac,
 					  u16 tx_airtime, bool tx_completed);
-void ieee80211_register_airtime(struct ieee80211_txq *txq,
-				u32 tx_airtime, u32 rx_airtime);
 
 struct sta_info;
 
@@ -607,6 +600,7 @@ struct link_sta_info {
  * @tid_seq: per-TID sequence numbers for sending to this STA
  * @airtime: per-AC struct airtime_info describing airtime statistics for this
  *	station
+ * @airtime_weight: station weight for airtime fairness calculation purposes
  * @ampdu_mlme: A-MPDU state machine state
  * @mesh: mesh STA information
  * @debugfs_dir: debug filesystem directory dentry
@@ -691,6 +685,7 @@ struct sta_info {
 	u16 tid_seq[IEEE80211_QOS_CTL_TID_MASK + 1];
 
 	struct airtime_info airtime[IEEE80211_NUM_ACS];
+	u16 airtime_weight;
 
 	/*
 	 * Aggregation information, locked with lock.
diff --git a/net/mac80211/status.c b/net/mac80211/status.c
index 5c2202a7ea1c..9bd4d336d444 100644
--- a/net/mac80211/status.c
+++ b/net/mac80211/status.c
@@ -998,25 +998,6 @@ static void __ieee80211_tx_status(struct ieee80211_hw *hw,
 		if (!(info->flags & IEEE80211_TX_CTL_INJECTED) && acked)
 			ieee80211_frame_acked(sta, skb);
 
-	} else if (wiphy_ext_feature_isset(local->hw.wiphy,
-					   NL80211_EXT_FEATURE_AIRTIME_FAIRNESS)) {
-		struct ieee80211_sub_if_data *sdata;
-		struct ieee80211_txq *txq;
-		u32 airtime;
-
-		/* Account airtime to multicast queue */
-		sdata = ieee80211_sdata_from_skb(local, skb);
-
-		if (sdata && (txq = sdata->vif.txq)) {
-			airtime = info->status.tx_time ?:
-				ieee80211_calc_expected_tx_airtime(hw,
-								   &sdata->vif,
-								   NULL,
-								   skb->len,
-								   false);
-
-			ieee80211_register_airtime(txq, airtime, 0);
-		}
 	}
 
 	/* SNMP counters
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index c3e14ef20c05..fcee60ce2456 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -18,7 +18,6 @@
 #include <linux/bitmap.h>
 #include <linux/rcupdate.h>
 #include <linux/export.h>
-#include <linux/timekeeping.h>
 #include <net/net_namespace.h>
 #include <net/ieee80211_radiotap.h>
 #include <net/cfg80211.h>
@@ -1479,7 +1478,7 @@ void ieee80211_txq_init(struct ieee80211_sub_if_data *sdata,
 	codel_vars_init(&txqi->def_cvars);
 	codel_stats_init(&txqi->cstats);
 	__skb_queue_head_init(&txqi->frags);
-	RB_CLEAR_NODE(&txqi->schedule_order);
+	INIT_LIST_HEAD(&txqi->schedule_order);
 
 	txqi->txq.vif = &sdata->vif;
 
@@ -1523,7 +1522,9 @@ void ieee80211_txq_purge(struct ieee80211_local *local,
 	ieee80211_purge_tx_queue(&local->hw, &txqi->frags);
 	spin_unlock_bh(&fq->lock);
 
-	ieee80211_unschedule_txq(&local->hw, &txqi->txq, true);
+	spin_lock_bh(&local->active_txq_lock[txqi->txq.ac]);
+	list_del_init(&txqi->schedule_order);
+	spin_unlock_bh(&local->active_txq_lock[txqi->txq.ac]);
 }
 
 void ieee80211_txq_set_params(struct ieee80211_local *local)
@@ -3802,259 +3803,102 @@ EXPORT_SYMBOL(ieee80211_tx_dequeue);
 struct ieee80211_txq *ieee80211_next_txq(struct ieee80211_hw *hw, u8 ac)
 {
 	struct ieee80211_local *local = hw_to_local(hw);
-	struct airtime_sched_info *air_sched;
-	u64 now = ktime_get_coarse_boottime_ns();
 	struct ieee80211_txq *ret = NULL;
-	struct airtime_info *air_info;
-	struct txq_info *txqi = NULL;
-	struct rb_node *node;
-	bool first = false;
+	struct txq_info *txqi = NULL, *head = NULL;
+	bool found_eligible_txq = false;
 
-	air_sched = &local->airtime[ac];
-	spin_lock_bh(&air_sched->lock);
+	spin_lock_bh(&local->active_txq_lock[ac]);
 
-	node = air_sched->schedule_pos;
-
-begin:
-	if (!node) {
-		node = rb_first_cached(&air_sched->active_txqs);
-		first = true;
-	} else {
-		node = rb_next(node);
-	}
-
-	if (!node)
-		goto out;
-
-	txqi = container_of(node, struct txq_info, schedule_order);
-	air_info = to_airtime_info(&txqi->txq);
-
-	if (air_info->v_t > air_sched->v_t &&
-	    (!first || !airtime_catchup_v_t(air_sched, air_info->v_t, now)))
+ begin:
+	txqi = list_first_entry_or_null(&local->active_txqs[ac],
+					struct txq_info,
+					schedule_order);
+	if (!txqi)
 		goto out;
 
-	if (!ieee80211_txq_airtime_check(hw, &txqi->txq)) {
-		first = false;
-		goto begin;
-	}
-
-	air_sched->schedule_pos = node;
-	air_sched->last_schedule_activity = now;
-	ret = &txqi->txq;
-out:
-	spin_unlock_bh(&air_sched->lock);
-	return ret;
-}
-EXPORT_SYMBOL(ieee80211_next_txq);
-
-static void __ieee80211_insert_txq(struct rb_root_cached *root,
-				   struct txq_info *txqi)
-{
-	struct rb_node **new = &root->rb_root.rb_node;
-	struct airtime_info *old_air, *new_air;
-	struct rb_node *parent = NULL;
-	struct txq_info *__txqi;
-	bool leftmost = true;
-
-	while (*new) {
-		parent = *new;
-		__txqi = rb_entry(parent, struct txq_info, schedule_order);
-		old_air = to_airtime_info(&__txqi->txq);
-		new_air = to_airtime_info(&txqi->txq);
-
-		if (new_air->v_t <= old_air->v_t) {
-			new = &parent->rb_left;
-		} else {
-			new = &parent->rb_right;
-			leftmost = false;
-		}
+	if (txqi == head) {
+		if (!found_eligible_txq)
+			goto out;
+		else
+			found_eligible_txq = false;
 	}
 
-	rb_link_node(&txqi->schedule_order, parent, new);
-	rb_insert_color_cached(&txqi->schedule_order, root, leftmost);
-}
+	if (!head)
+		head = txqi;
 
-void ieee80211_resort_txq(struct ieee80211_hw *hw,
-			  struct ieee80211_txq *txq)
-{
-	struct airtime_info *air_info = to_airtime_info(txq);
-	struct ieee80211_local *local = hw_to_local(hw);
-	struct txq_info *txqi = to_txq_info(txq);
-	struct airtime_sched_info *air_sched;
-
-	air_sched = &local->airtime[txq->ac];
-
-	lockdep_assert_held(&air_sched->lock);
+	if (txqi->txq.sta) {
+		struct sta_info *sta = container_of(txqi->txq.sta,
+						    struct sta_info, sta);
+		bool aql_check = ieee80211_txq_airtime_check(hw, &txqi->txq);
+		s64 deficit = sta->airtime[txqi->txq.ac].deficit;
 
-	if (!RB_EMPTY_NODE(&txqi->schedule_order)) {
-		struct airtime_info *a_prev = NULL, *a_next = NULL;
-		struct txq_info *t_prev, *t_next;
-		struct rb_node *n_prev, *n_next;
+		if (aql_check)
+			found_eligible_txq = true;
 
-		/* Erasing a node can cause an expensive rebalancing operation,
-		 * so we check the previous and next nodes first and only remove
-		 * and re-insert if the current node is not already in the
-		 * correct position.
-		 */
-		if ((n_prev = rb_prev(&txqi->schedule_order)) != NULL) {
-			t_prev = container_of(n_prev, struct txq_info,
-					      schedule_order);
-			a_prev = to_airtime_info(&t_prev->txq);
-		}
+		if (deficit < 0)
+			sta->airtime[txqi->txq.ac].deficit +=
+				sta->airtime_weight;
 
-		if ((n_next = rb_next(&txqi->schedule_order)) != NULL) {
-			t_next = container_of(n_next, struct txq_info,
-					      schedule_order);
-			a_next = to_airtime_info(&t_next->txq);
+		if (deficit < 0 || !aql_check) {
+			list_move_tail(&txqi->schedule_order,
+				       &local->active_txqs[txqi->txq.ac]);
+			goto begin;
 		}
-
-		if ((!a_prev || a_prev->v_t <= air_info->v_t) &&
-		    (!a_next || a_next->v_t > air_info->v_t))
-			return;
-
-		if (air_sched->schedule_pos == &txqi->schedule_order)
-			air_sched->schedule_pos = n_prev;
-
-		rb_erase_cached(&txqi->schedule_order,
-				&air_sched->active_txqs);
-		RB_CLEAR_NODE(&txqi->schedule_order);
-		__ieee80211_insert_txq(&air_sched->active_txqs, txqi);
 	}
-}
 
-void ieee80211_update_airtime_weight(struct ieee80211_local *local,
-				     struct airtime_sched_info *air_sched,
-				     u64 now, bool force)
-{
-	struct airtime_info *air_info, *tmp;
-	u64 weight_sum = 0;
-
-	if (unlikely(!now))
-		now = ktime_get_coarse_boottime_ns();
 
-	lockdep_assert_held(&air_sched->lock);
-
-	if (!force && (air_sched->last_weight_update <
-		       now - AIRTIME_ACTIVE_DURATION))
-		return;
-
-	list_for_each_entry_safe(air_info, tmp,
-				 &air_sched->active_list, list) {
-		if (airtime_is_active(air_info, now))
-			weight_sum += air_info->weight;
-		else
-			list_del_init(&air_info->list);
-	}
-	airtime_weight_sum_set(air_sched, weight_sum);
-	air_sched->last_weight_update = now;
-}
-
-void ieee80211_schedule_txq(struct ieee80211_hw *hw,
-			    struct ieee80211_txq *txq)
-	__acquires(txq_lock) __releases(txq_lock)
-{
-	struct ieee80211_local *local = hw_to_local(hw);
-	struct txq_info *txqi = to_txq_info(txq);
-	struct airtime_sched_info *air_sched;
-	u64 now = ktime_get_coarse_boottime_ns();
-	struct airtime_info *air_info;
-	u8 ac = txq->ac;
-	bool was_active;
-
-	air_sched = &local->airtime[ac];
-	air_info = to_airtime_info(txq);
-
-	spin_lock_bh(&air_sched->lock);
-	was_active = airtime_is_active(air_info, now);
-	airtime_set_active(air_sched, air_info, now);
-
-	if (!RB_EMPTY_NODE(&txqi->schedule_order))
+	if (txqi->schedule_round == local->schedule_round[ac])
 		goto out;
 
-	/* If the station has been inactive for a while, catch up its v_t so it
-	 * doesn't get indefinite priority; see comment above the definition of
-	 * AIRTIME_MAX_BEHIND.
-	 */
-	if ((!was_active && air_info->v_t < air_sched->v_t) ||
-	    air_info->v_t < air_sched->v_t - AIRTIME_MAX_BEHIND)
-		air_info->v_t = air_sched->v_t;
-
-	ieee80211_update_airtime_weight(local, air_sched, now, !was_active);
-	__ieee80211_insert_txq(&air_sched->active_txqs, txqi);
+	list_del_init(&txqi->schedule_order);
+	txqi->schedule_round = local->schedule_round[ac];
+	ret = &txqi->txq;
 
 out:
-	spin_unlock_bh(&air_sched->lock);
-}
-EXPORT_SYMBOL(ieee80211_schedule_txq);
-
-static void __ieee80211_unschedule_txq(struct ieee80211_hw *hw,
-				       struct ieee80211_txq *txq,
-				       bool purge)
-{
-	struct ieee80211_local *local = hw_to_local(hw);
-	struct txq_info *txqi = to_txq_info(txq);
-	struct airtime_sched_info *air_sched;
-	struct airtime_info *air_info;
-
-	air_sched = &local->airtime[txq->ac];
-	air_info = to_airtime_info(&txqi->txq);
-
-	lockdep_assert_held(&air_sched->lock);
-
-	if (purge) {
-		list_del_init(&air_info->list);
-		ieee80211_update_airtime_weight(local, air_sched, 0, true);
-	}
-
-	if (RB_EMPTY_NODE(&txqi->schedule_order))
-		return;
-
-	if (air_sched->schedule_pos == &txqi->schedule_order)
-		air_sched->schedule_pos = rb_prev(&txqi->schedule_order);
-
-	if (!purge)
-		airtime_set_active(air_sched, air_info,
-				   ktime_get_coarse_boottime_ns());
-
-	rb_erase_cached(&txqi->schedule_order,
-			&air_sched->active_txqs);
-	RB_CLEAR_NODE(&txqi->schedule_order);
+	spin_unlock_bh(&local->active_txq_lock[ac]);
+	return ret;
 }
+EXPORT_SYMBOL(ieee80211_next_txq);
 
-void ieee80211_unschedule_txq(struct ieee80211_hw *hw,
+void __ieee80211_schedule_txq(struct ieee80211_hw *hw,
 			      struct ieee80211_txq *txq,
-			      bool purge)
-	__acquires(txq_lock) __releases(txq_lock)
-{
-	struct ieee80211_local *local = hw_to_local(hw);
-
-	spin_lock_bh(&local->airtime[txq->ac].lock);
-	__ieee80211_unschedule_txq(hw, txq, purge);
-	spin_unlock_bh(&local->airtime[txq->ac].lock);
-}
-
-void ieee80211_return_txq(struct ieee80211_hw *hw,
-			  struct ieee80211_txq *txq, bool force)
+			      bool force)
 {
 	struct ieee80211_local *local = hw_to_local(hw);
 	struct txq_info *txqi = to_txq_info(txq);
 
-	spin_lock_bh(&local->airtime[txq->ac].lock);
-
-	if (!RB_EMPTY_NODE(&txqi->schedule_order) && !force &&
-	    !txq_has_queue(txq))
-		__ieee80211_unschedule_txq(hw, txq, false);
+	spin_lock_bh(&local->active_txq_lock[txq->ac]);
+
+	if (list_empty(&txqi->schedule_order) &&
+	    (force || !skb_queue_empty(&txqi->frags) ||
+	     txqi->tin.backlog_packets)) {
+		/* If airtime accounting is active, always enqueue STAs at the
+		 * head of the list to ensure that they only get moved to the
+		 * back by the airtime DRR scheduler once they have a negative
+		 * deficit. A station that already has a negative deficit will
+		 * get immediately moved to the back of the list on the next
+		 * call to ieee80211_next_txq().
+		 */
+		if (txqi->txq.sta && local->airtime_flags &&
+		    wiphy_ext_feature_isset(local->hw.wiphy,
+					    NL80211_EXT_FEATURE_AIRTIME_FAIRNESS))
+			list_add(&txqi->schedule_order,
+				 &local->active_txqs[txq->ac]);
+		else
+			list_add_tail(&txqi->schedule_order,
+				      &local->active_txqs[txq->ac]);
+	}
 
-	spin_unlock_bh(&local->airtime[txq->ac].lock);
+	spin_unlock_bh(&local->active_txq_lock[txq->ac]);
 }
-EXPORT_SYMBOL(ieee80211_return_txq);
+EXPORT_SYMBOL(__ieee80211_schedule_txq);
 
 DEFINE_STATIC_KEY_FALSE(aql_disable);
 
 bool ieee80211_txq_airtime_check(struct ieee80211_hw *hw,
 				 struct ieee80211_txq *txq)
 {
-	struct airtime_info *air_info = to_airtime_info(txq);
+	struct sta_info *sta;
 	struct ieee80211_local *local = hw_to_local(hw);
 
 	if (!wiphy_ext_feature_isset(local->hw.wiphy, NL80211_EXT_FEATURE_AQL))
@@ -4069,12 +3913,15 @@ bool ieee80211_txq_airtime_check(struct ieee80211_hw *hw,
 	if (unlikely(txq->tid == IEEE80211_NUM_TIDS))
 		return true;
 
-	if (atomic_read(&air_info->aql_tx_pending) < air_info->aql_limit_low)
+	sta = container_of(txq->sta, struct sta_info, sta);
+	if (atomic_read(&sta->airtime[txq->ac].aql_tx_pending) <
+	    sta->airtime[txq->ac].aql_limit_low)
 		return true;
 
 	if (atomic_read(&local->aql_total_pending_airtime) <
 	    local->aql_threshold &&
-	    atomic_read(&air_info->aql_tx_pending) < air_info->aql_limit_high)
+	    atomic_read(&sta->airtime[txq->ac].aql_tx_pending) <
+	    sta->airtime[txq->ac].aql_limit_high)
 		return true;
 
 	return false;
@@ -4084,59 +3931,60 @@ EXPORT_SYMBOL(ieee80211_txq_airtime_check);
 bool ieee80211_txq_may_transmit(struct ieee80211_hw *hw,
 				struct ieee80211_txq *txq)
 {
-	struct txq_info *first_txqi = NULL, *txqi = to_txq_info(txq);
 	struct ieee80211_local *local = hw_to_local(hw);
-	struct airtime_sched_info *air_sched;
-	struct airtime_info *air_info;
-	struct rb_node *node = NULL;
-	bool ret = false;
-	u64 now;
-
-
-	if (!ieee80211_txq_airtime_check(hw, txq))
-		return false;
+	struct txq_info *iter, *tmp, *txqi = to_txq_info(txq);
+	struct sta_info *sta;
+	u8 ac = txq->ac;
 
-	air_sched = &local->airtime[txq->ac];
-	spin_lock_bh(&air_sched->lock);
+	spin_lock_bh(&local->active_txq_lock[ac]);
 
-	if (RB_EMPTY_NODE(&txqi->schedule_order))
+	if (!txqi->txq.sta)
 		goto out;
 
-	now = ktime_get_coarse_boottime_ns();
+	if (list_empty(&txqi->schedule_order))
+		goto out;
 
-	/* Like in ieee80211_next_txq(), make sure the first station in the
-	 * scheduling order is eligible for transmission to avoid starvation.
-	 */
-	node = rb_first_cached(&air_sched->active_txqs);
-	if (node) {
-		first_txqi = container_of(node, struct txq_info,
-					  schedule_order);
-		air_info = to_airtime_info(&first_txqi->txq);
+	list_for_each_entry_safe(iter, tmp, &local->active_txqs[ac],
+				 schedule_order) {
+		if (iter == txqi)
+			break;
 
-		if (air_sched->v_t < air_info->v_t)
-			airtime_catchup_v_t(air_sched, air_info->v_t, now);
+		if (!iter->txq.sta) {
+			list_move_tail(&iter->schedule_order,
+				       &local->active_txqs[ac]);
+			continue;
+		}
+		sta = container_of(iter->txq.sta, struct sta_info, sta);
+		if (sta->airtime[ac].deficit < 0)
+			sta->airtime[ac].deficit += sta->airtime_weight;
+		list_move_tail(&iter->schedule_order, &local->active_txqs[ac]);
 	}
 
-	air_info = to_airtime_info(&txqi->txq);
-	if (air_info->v_t <= air_sched->v_t) {
-		air_sched->last_schedule_activity = now;
-		ret = true;
-	}
+	sta = container_of(txqi->txq.sta, struct sta_info, sta);
+	if (sta->airtime[ac].deficit >= 0)
+		goto out;
+
+	sta->airtime[ac].deficit += sta->airtime_weight;
+	list_move_tail(&txqi->schedule_order, &local->active_txqs[ac]);
+	spin_unlock_bh(&local->active_txq_lock[ac]);
 
+	return false;
 out:
-	spin_unlock_bh(&air_sched->lock);
-	return ret;
+	if (!list_empty(&txqi->schedule_order))
+		list_del_init(&txqi->schedule_order);
+	spin_unlock_bh(&local->active_txq_lock[ac]);
+
+	return true;
 }
 EXPORT_SYMBOL(ieee80211_txq_may_transmit);
 
 void ieee80211_txq_schedule_start(struct ieee80211_hw *hw, u8 ac)
 {
 	struct ieee80211_local *local = hw_to_local(hw);
-	struct airtime_sched_info *air_sched = &local->airtime[ac];
 
-	spin_lock_bh(&air_sched->lock);
-	air_sched->schedule_pos = NULL;
-	spin_unlock_bh(&air_sched->lock);
+	spin_lock_bh(&local->active_txq_lock[ac]);
+	local->schedule_round[ac]++;
+	spin_unlock_bh(&local->active_txq_lock[ac]);
 }
 EXPORT_SYMBOL(ieee80211_txq_schedule_start);
 
-- 
2.36.1

[PATCH 2/7] mac80211: make sta airtime deficit field s32 instead of s64

[Felix Fietkau]

32 bit is more than enough range for the airtime deficit

Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 net/mac80211/debugfs_sta.c | 4 ++--
 net/mac80211/sta_info.h    | 2 +-
 net/mac80211/tx.c          | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/mac80211/debugfs_sta.c b/net/mac80211/debugfs_sta.c
index 1dc238fc24f0..d3397c1248d3 100644
--- a/net/mac80211/debugfs_sta.c
+++ b/net/mac80211/debugfs_sta.c
@@ -202,7 +202,7 @@ static ssize_t sta_airtime_read(struct file *file, char __user *userbuf,
 	size_t bufsz = 400;
 	char *buf = kzalloc(bufsz, GFP_KERNEL), *p = buf;
 	u64 rx_airtime = 0, tx_airtime = 0;
-	s64 deficit[IEEE80211_NUM_ACS];
+	s32 deficit[IEEE80211_NUM_ACS];
 	ssize_t rv;
 	int ac;
 
@@ -219,7 +219,7 @@ static ssize_t sta_airtime_read(struct file *file, char __user *userbuf,
 
 	p += scnprintf(p, bufsz + buf - p,
 		"RX: %llu us\nTX: %llu us\nWeight: %u\n"
-		"Deficit: VO: %lld us VI: %lld us BE: %lld us BK: %lld us\n",
+		"Deficit: VO: %d us VI: %d us BE: %d us BK: %d us\n",
 		rx_airtime, tx_airtime, sta->airtime_weight,
 		deficit[0], deficit[1], deficit[2], deficit[3]);
 
diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index 4ba0c252da95..785fefe8c41a 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -138,7 +138,7 @@ enum ieee80211_agg_stop_reason {
 struct airtime_info {
 	u64 rx_airtime;
 	u64 tx_airtime;
-	s64 deficit;
+	s32 deficit;
 	atomic_t aql_tx_pending; /* Estimated airtime for frames pending */
 	u32 aql_limit_low;
 	u32 aql_limit_high;
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index fcee60ce2456..a615cadf7728 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -3830,7 +3830,7 @@ struct ieee80211_txq *ieee80211_next_txq(struct ieee80211_hw *hw, u8 ac)
 		struct sta_info *sta = container_of(txqi->txq.sta,
 						    struct sta_info, sta);
 		bool aql_check = ieee80211_txq_airtime_check(hw, &txqi->txq);
-		s64 deficit = sta->airtime[txqi->txq.ac].deficit;
+		s32 deficit = sta->airtime[txqi->txq.ac].deficit;
 
 		if (aql_check)
 			found_eligible_txq = true;
-- 
2.36.1

[PATCH 3/7] mac80211: consider aql_tx_pending when checking airtime deficit

[Felix Fietkau]

When queueing packets for a station, deficit only gets added once the packets
have been transmitted, which could be much later. During that time, a lot of
temporary unfairness could happen, which could lead to bursty behavior.
Fix this by subtracting the aql_tx_pending when checking the deficit in tx
scheduling.

Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 net/mac80211/tx.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index a615cadf7728..0509486ac40a 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -3800,6 +3800,13 @@ struct sk_buff *ieee80211_tx_dequeue(struct ieee80211_hw *hw,
 }
 EXPORT_SYMBOL(ieee80211_tx_dequeue);
 
+static inline s32 ieee80211_sta_deficit(struct sta_info *sta, u8 ac)
+{
+	struct airtime_info *air_info = &sta->airtime[ac];
+
+	return air_info->deficit - atomic_read(&air_info->aql_tx_pending);
+}
+
 struct ieee80211_txq *ieee80211_next_txq(struct ieee80211_hw *hw, u8 ac)
 {
 	struct ieee80211_local *local = hw_to_local(hw);
@@ -3830,7 +3837,7 @@ struct ieee80211_txq *ieee80211_next_txq(struct ieee80211_hw *hw, u8 ac)
 		struct sta_info *sta = container_of(txqi->txq.sta,
 						    struct sta_info, sta);
 		bool aql_check = ieee80211_txq_airtime_check(hw, &txqi->txq);
-		s32 deficit = sta->airtime[txqi->txq.ac].deficit;
+		s32 deficit = ieee80211_sta_deficit(sta, txqi->txq.ac);
 
 		if (aql_check)
 			found_eligible_txq = true;
@@ -3955,7 +3962,7 @@ bool ieee80211_txq_may_transmit(struct ieee80211_hw *hw,
 			continue;
 		}
 		sta = container_of(iter->txq.sta, struct sta_info, sta);
-		if (sta->airtime[ac].deficit < 0)
+		if (ieee80211_sta_deficit(sta, ac) < 0)
 			sta->airtime[ac].deficit += sta->airtime_weight;
 		list_move_tail(&iter->schedule_order, &local->active_txqs[ac]);
 	}
-- 
2.36.1

[PATCH 4/7] mac80211: keep recently active tx queues in scheduling list

[Felix Fietkau]

This allows proper deficit accounting to ensure that they don't carry their
deficit until the next time they become active

Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 net/mac80211/ieee80211_i.h |  7 +++++++
 net/mac80211/sta_info.h    |  1 +
 net/mac80211/tx.c          | 40 ++++++++++++++++++++++++++++++++++----
 3 files changed, 44 insertions(+), 4 deletions(-)

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 8ef27e0f9371..c5a76bec03a4 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -83,6 +83,13 @@ extern const u8 ieee80211_ac_to_qos_mask[IEEE80211_NUM_ACS];
 
 #define IEEE80211_MAX_NAN_INSTANCE_ID 255
 
+
+/*
+ * Keep a station's queues on the active list for deficit accounting purposes
+ * if it was active or queued during the last 100ms
+ */
+#define AIRTIME_ACTIVE_DURATION (HZ / 10)
+
 struct ieee80211_bss {
 	u32 device_ts_beacon, device_ts_presp;
 
diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index 785fefe8c41a..aa599f82b065 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -138,6 +138,7 @@ enum ieee80211_agg_stop_reason {
 struct airtime_info {
 	u64 rx_airtime;
 	u64 tx_airtime;
+	u32 last_active;
 	s32 deficit;
 	atomic_t aql_tx_pending; /* Estimated airtime for frames pending */
 	u32 aql_limit_low;
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 0509486ac40a..71c1d2a5eef3 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -3807,6 +3807,36 @@ static inline s32 ieee80211_sta_deficit(struct sta_info *sta, u8 ac)
 	return air_info->deficit - atomic_read(&air_info->aql_tx_pending);
 }
 
+static void
+ieee80211_txq_set_active(struct txq_info *txqi)
+{
+	struct sta_info *sta;
+
+	if (!txqi->txq.sta)
+		return;
+
+	sta = container_of(txqi->txq.sta, struct sta_info, sta);
+	sta->airtime[txqi->txq.ac].last_active = (u32)jiffies;
+}
+
+static bool
+ieee80211_txq_keep_active(struct txq_info *txqi)
+{
+	struct sta_info *sta;
+	u32 diff;
+
+	if (!txqi->txq.sta)
+		return false;
+
+	sta = container_of(txqi->txq.sta, struct sta_info, sta);
+	if (ieee80211_sta_deficit(sta, txqi->txq.ac) >= 0)
+		return false;
+
+	diff = (u32)jiffies - sta->airtime[txqi->txq.ac].last_active;
+
+	return diff <= AIRTIME_ACTIVE_DURATION;
+}
+
 struct ieee80211_txq *ieee80211_next_txq(struct ieee80211_hw *hw, u8 ac)
 {
 	struct ieee80211_local *local = hw_to_local(hw);
@@ -3853,7 +3883,6 @@ struct ieee80211_txq *ieee80211_next_txq(struct ieee80211_hw *hw, u8 ac)
 		}
 	}
 
-
 	if (txqi->schedule_round == local->schedule_round[ac])
 		goto out;
 
@@ -3873,12 +3902,13 @@ void __ieee80211_schedule_txq(struct ieee80211_hw *hw,
 {
 	struct ieee80211_local *local = hw_to_local(hw);
 	struct txq_info *txqi = to_txq_info(txq);
+	bool has_queue;
 
 	spin_lock_bh(&local->active_txq_lock[txq->ac]);
 
+	has_queue = force || txq_has_queue(txq);
 	if (list_empty(&txqi->schedule_order) &&
-	    (force || !skb_queue_empty(&txqi->frags) ||
-	     txqi->tin.backlog_packets)) {
+	    (has_queue || ieee80211_txq_keep_active(txqi))) {
 		/* If airtime accounting is active, always enqueue STAs at the
 		 * head of the list to ensure that they only get moved to the
 		 * back by the airtime DRR scheduler once they have a negative
@@ -3886,7 +3916,7 @@ void __ieee80211_schedule_txq(struct ieee80211_hw *hw,
 		 * get immediately moved to the back of the list on the next
 		 * call to ieee80211_next_txq().
 		 */
-		if (txqi->txq.sta && local->airtime_flags &&
+		if (txqi->txq.sta && local->airtime_flags && has_queue &&
 		    wiphy_ext_feature_isset(local->hw.wiphy,
 					    NL80211_EXT_FEATURE_AIRTIME_FAIRNESS))
 			list_add(&txqi->schedule_order,
@@ -3894,6 +3924,8 @@ void __ieee80211_schedule_txq(struct ieee80211_hw *hw,
 		else
 			list_add_tail(&txqi->schedule_order,
 				      &local->active_txqs[txq->ac]);
+		if (has_queue)
+			ieee80211_txq_set_active(txqi);
 	}
 
 	spin_unlock_bh(&local->active_txq_lock[txq->ac]);
-- 
2.36.1

[PATCH 5/7] mac80211: add a per-PHY AQL limit to improve fairness

[Felix Fietkau]

In order to maintain fairness, the amount of queueing needs to be limited
beyond the simple per-station AQL budget, otherwise the driver can simply
repeatedly do scheduling rounds until all queues that have not used their
AQL budget become eligble.

To be conservative, use the high AQL limit for the first txq and add half
of the low AQL for each subsequent queue.

Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 net/mac80211/ieee80211_i.h |  1 +
 net/mac80211/main.c        |  1 +
 net/mac80211/sta_info.c    | 10 +++++++---
 net/mac80211/tx.c          | 35 ++++++++++++++++++++++++++++++++++-
 4 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index c5a76bec03a4..7c199bd66f73 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -1239,6 +1239,7 @@ struct ieee80211_local {
 	u32 aql_txq_limit_high[IEEE80211_NUM_ACS];
 	u32 aql_threshold;
 	atomic_t aql_total_pending_airtime;
+	atomic_t aql_ac_pending_airtime[IEEE80211_NUM_ACS];
 
 	const struct ieee80211_ops *ops;
 
diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index e6c1cafbe9e5..929bbdf55213 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -789,6 +789,7 @@ struct ieee80211_hw *ieee80211_alloc_hw_nm(size_t priv_data_len,
 		local->aql_txq_limit_low[i] = IEEE80211_DEFAULT_AQL_TXQ_LIMIT_L;
 		local->aql_txq_limit_high[i] =
 			IEEE80211_DEFAULT_AQL_TXQ_LIMIT_H;
+		atomic_set(&local->aql_ac_pending_airtime[i], 0);
 	}
 
 	local->airtime_flags = AIRTIME_USE_TX | AIRTIME_USE_RX;
diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index a1a2118b4bf0..28ab55a072c6 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -2075,6 +2075,7 @@ void ieee80211_sta_update_pending_airtime(struct ieee80211_local *local,
 				   &sta->airtime[ac].aql_tx_pending);
 
 		atomic_add(tx_airtime, &local->aql_total_pending_airtime);
+		atomic_add(tx_airtime, &local->aql_ac_pending_airtime[ac]);
 		return;
 	}
 
@@ -2086,14 +2087,17 @@ void ieee80211_sta_update_pending_airtime(struct ieee80211_local *local,
 				       tx_pending, 0);
 	}
 
+	atomic_sub(tx_airtime, &local->aql_total_pending_airtime);
 	tx_pending = atomic_sub_return(tx_airtime,
-				       &local->aql_total_pending_airtime);
+				       &local->aql_ac_pending_airtime[ac]);
 	if (WARN_ONCE(tx_pending < 0,
 		      "Device %s AC %d pending airtime underflow: %u, %u",
 		      wiphy_name(local->hw.wiphy), ac, tx_pending,
-		      tx_airtime))
-		atomic_cmpxchg(&local->aql_total_pending_airtime,
+		      tx_airtime)) {
+		atomic_cmpxchg(&local->aql_ac_pending_airtime[ac],
 			       tx_pending, 0);
+		atomic_sub(tx_pending, &local->aql_total_pending_airtime);
+	}
 }
 
 int sta_info_move_state(struct sta_info *sta,
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 71c1d2a5eef3..b2430cf8332b 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -3846,6 +3846,9 @@ struct ieee80211_txq *ieee80211_next_txq(struct ieee80211_hw *hw, u8 ac)
 
 	spin_lock_bh(&local->active_txq_lock[ac]);
 
+	if (!local->schedule_round[ac])
+		goto out;
+
  begin:
 	txqi = list_first_entry_or_null(&local->active_txqs[ac],
 					struct txq_info,
@@ -3967,6 +3970,25 @@ bool ieee80211_txq_airtime_check(struct ieee80211_hw *hw,
 }
 EXPORT_SYMBOL(ieee80211_txq_airtime_check);
 
+static bool
+ieee80211_txq_schedule_airtime_check(struct ieee80211_local *local, u8 ac)
+{
+	unsigned int num_txq = 0;
+	struct txq_info *txq;
+	u32 aql_limit;
+
+	if (!wiphy_ext_feature_isset(local->hw.wiphy, NL80211_EXT_FEATURE_AQL))
+		return true;
+
+	list_for_each_entry(txq, &local->active_txqs[ac], schedule_order)
+		num_txq++;
+
+	aql_limit = (num_txq - 1) * local->aql_txq_limit_low[ac] / 2 +
+		    local->aql_txq_limit_high[ac];
+
+	return atomic_read(&local->aql_ac_pending_airtime[ac]) < aql_limit;
+}
+
 bool ieee80211_txq_may_transmit(struct ieee80211_hw *hw,
 				struct ieee80211_txq *txq)
 {
@@ -3983,6 +4005,9 @@ bool ieee80211_txq_may_transmit(struct ieee80211_hw *hw,
 	if (list_empty(&txqi->schedule_order))
 		goto out;
 
+	if (!ieee80211_txq_schedule_airtime_check(local, ac))
+		goto out;
+
 	list_for_each_entry_safe(iter, tmp, &local->active_txqs[ac],
 				 schedule_order) {
 		if (iter == txqi)
@@ -4022,7 +4047,15 @@ void ieee80211_txq_schedule_start(struct ieee80211_hw *hw, u8 ac)
 	struct ieee80211_local *local = hw_to_local(hw);
 
 	spin_lock_bh(&local->active_txq_lock[ac]);
-	local->schedule_round[ac]++;
+
+	if (ieee80211_txq_schedule_airtime_check(local, ac)) {
+		local->schedule_round[ac]++;
+		if (!local->schedule_round[ac])
+			local->schedule_round[ac]++;
+	} else {
+		local->schedule_round[ac] = 0;
+	}
+
 	spin_unlock_bh(&local->active_txq_lock[ac]);
 }
 EXPORT_SYMBOL(ieee80211_txq_schedule_start);
-- 
2.36.1

[PATCH 6/7] mac80211: add debugfs file to display per-phy AQL pending airtime

[Felix Fietkau]

Now that the global pending airtime is more relevant for airtime fairness,
it makes sense to make it accessible via debugfs for debugging

Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 net/mac80211/debugfs.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/net/mac80211/debugfs.c b/net/mac80211/debugfs.c
index 0c748b1eb023..4d4341249759 100644
--- a/net/mac80211/debugfs.c
+++ b/net/mac80211/debugfs.c
@@ -201,6 +201,36 @@ static const struct file_operations airtime_flags_ops = {
 	.llseek = default_llseek,
 };
 
+static ssize_t aql_pending_read(struct file *file,
+				char __user *user_buf,
+				size_t count, loff_t *ppos)
+{
+	struct ieee80211_local *local = file->private_data;
+	char buf[400];
+	int len = 0;
+
+	len = scnprintf(buf, sizeof(buf),
+			"AC     AQL pending\n"
+			"VO     %u us\n"
+			"VI     %u us\n"
+			"BE     %u us\n"
+			"BK     %u us\n"
+			"total  %u us\n",
+			atomic_read(&local->aql_ac_pending_airtime[IEEE80211_AC_VO]),
+			atomic_read(&local->aql_ac_pending_airtime[IEEE80211_AC_VI]),
+			atomic_read(&local->aql_ac_pending_airtime[IEEE80211_AC_BE]),
+			atomic_read(&local->aql_ac_pending_airtime[IEEE80211_AC_BK]),
+			atomic_read(&local->aql_total_pending_airtime));
+	return simple_read_from_buffer(user_buf, count, ppos,
+				       buf, len);
+}
+
+static const struct file_operations aql_pending_ops = {
+	.read = aql_pending_read,
+	.open = simple_open,
+	.llseek = default_llseek,
+};
+
 static ssize_t aql_txq_limit_read(struct file *file,
 				  char __user *user_buf,
 				  size_t count,
@@ -631,6 +661,7 @@ void debugfs_hw_add(struct ieee80211_local *local)
 	DEBUGFS_ADD(hw_conf);
 	DEBUGFS_ADD_MODE(force_tx_status, 0600);
 	DEBUGFS_ADD_MODE(aql_enable, 0600);
+	DEBUGFS_ADD(aql_pending);
 
 	if (local->ops->wake_tx_queue)
 		DEBUGFS_ADD_MODE(aqm, 0600);
-- 
2.36.1

[PATCH 7/7] mac80211: only accumulate airtime deficit for active clients

[Felix Fietkau]

When a client does not generate any local tx activity, accumulating airtime
deficit for the round-robin scheduler can be harmful. If this goes on for too
long, the deficit could grow quite large, which might cause unreasonable
initial latency once the client becomes active

Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 net/mac80211/sta_info.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index 28ab55a072c6..c9852f71e8e1 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -2046,6 +2046,7 @@ void ieee80211_sta_register_airtime(struct ieee80211_sta *pubsta, u8 tid,
 	struct ieee80211_local *local = sta->sdata->local;
 	u8 ac = ieee80211_ac_from_tid(tid);
 	u32 airtime = 0;
+	u32 diff;
 
 	if (sta->local->airtime_flags & AIRTIME_USE_TX)
 		airtime += tx_airtime;
@@ -2055,7 +2056,11 @@ void ieee80211_sta_register_airtime(struct ieee80211_sta *pubsta, u8 tid,
 	spin_lock_bh(&local->active_txq_lock[ac]);
 	sta->airtime[ac].tx_airtime += tx_airtime;
 	sta->airtime[ac].rx_airtime += rx_airtime;
-	sta->airtime[ac].deficit -= airtime;
+
+	diff = (u32)jiffies - sta->airtime[ac].last_active;
+	if (diff <= AIRTIME_ACTIVE_DURATION)
+		sta->airtime[ac].deficit -= airtime;
+
 	spin_unlock_bh(&local->active_txq_lock[ac]);
 }
 EXPORT_SYMBOL(ieee80211_sta_register_airtime);
-- 
2.36.1

Re: [PATCH 1/7] mac80211: switch airtime fairness back to deficit round-robin scheduling

[Toke Høiland-Jørgensen]

Felix Fietkau <nbd@nbd.name> writes:

> This reverts commits 6a789ba679d652587532cec2a0e0274fda172f3b and
> 2433647bc8d983a543e7d31b41ca2de1c7e2c198.
>
> The virtual time scheduler code has a number of issues:
> - queues slowed down by hardware/firmware powersave handling were not properly
>   handled.
> - on ath10k in push-pull mode, tx queues that the driver tries to pull from
>   were starved, causing excessive latency
> - delay between tx enqueue and reported airtime use were causing excessively
>   bursty tx behavior
>
> The bursty behavior may also be present on the round-robin scheduler, but there
> it is much easier to fix without introducing additional regressions
>
> Signed-off-by: Felix Fietkau <nbd@nbd.name>

Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>

Re: [PATCH 2/7] mac80211: make sta airtime deficit field s32 instead of s64

[Toke Høiland-Jørgensen]

Felix Fietkau <nbd@nbd.name> writes:

> 32 bit is more than enough range for the airtime deficit
>
> Signed-off-by: Felix Fietkau <nbd@nbd.name>

Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>

Re: [PATCH 3/7] mac80211: consider aql_tx_pending when checking airtime deficit

[Toke Høiland-Jørgensen]

Felix Fietkau <nbd@nbd.name> writes:

> When queueing packets for a station, deficit only gets added once the packets
> have been transmitted, which could be much later. During that time, a lot of
> temporary unfairness could happen, which could lead to bursty behavior.
> Fix this by subtracting the aql_tx_pending when checking the deficit in tx
> scheduling.
>
> Signed-off-by: Felix Fietkau <nbd@nbd.name>

Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>

Re: [PATCH 4/7] mac80211: keep recently active tx queues in scheduling list

[Toke Høiland-Jørgensen]

Felix Fietkau <nbd@nbd.name> writes:

> This allows proper deficit accounting to ensure that they don't carry their
> deficit until the next time they become active
>
> Signed-off-by: Felix Fietkau <nbd@nbd.name>

Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>

Re: [PATCH 5/7] mac80211: add a per-PHY AQL limit to improve fairness

[Toke Høiland-Jørgensen]

Felix Fietkau <nbd@nbd.name> writes:

> In order to maintain fairness, the amount of queueing needs to be limited
> beyond the simple per-station AQL budget, otherwise the driver can simply
> repeatedly do scheduling rounds until all queues that have not used their
> AQL budget become eligble.
>
> To be conservative, use the high AQL limit for the first txq and add half
> of the low AQL for each subsequent queue.
>
> Signed-off-by: Felix Fietkau <nbd@nbd.name>

Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>

Re: [PATCH 6/7] mac80211: add debugfs file to display per-phy AQL pending airtime

[Toke Høiland-Jørgensen]

Felix Fietkau <nbd@nbd.name> writes:

> Now that the global pending airtime is more relevant for airtime fairness,
> it makes sense to make it accessible via debugfs for debugging
>
> Signed-off-by: Felix Fietkau <nbd@nbd.name>

Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>

Re: [PATCH 7/7] mac80211: only accumulate airtime deficit for active clients

[Toke Høiland-Jørgensen]

Felix Fietkau <nbd@nbd.name> writes:

> When a client does not generate any local tx activity, accumulating airtime
> deficit for the round-robin scheduler can be harmful. If this goes on for too
> long, the deficit could grow quite large, which might cause unreasonable
> initial latency once the client becomes active
>
> Signed-off-by: Felix Fietkau <nbd@nbd.name>

Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>