wifi: mac80211: switch airtime fairness back to deficit round-robin scheduling

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>
Link: https://lore.kernel.org/r/20220625212411.36675-1-nbd@nbd.name
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 18 insertions, 49 deletions

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);
 	}