From: =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= Date: Mon, 18 Nov 2019 22:06:10 -0800 Subject: [PATCH] mac80211: Use Airtime-based Queue Limits (AQL) on packet dequeue MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The previous commit added the ability to throttle stations when they queue too much airtime in the hardware. This commit enables the functionality by calculating the expected airtime usage of each packet that is dequeued from the TXQs in mac80211, and accounting that as pending airtime. The estimated airtime for each skb is stored in the tx_info, so we can subtract the same amount from the running total when the skb is freed or recycled. The throttling mechanism relies on this accounting to be accurate (i.e., that we are not freeing skbs without subtracting any airtime they were accounted for), so we put the subtraction into ieee80211_report_used_skb(). As an optimisation, we also subtract the airtime on regular TX completion, zeroing out the value stored in the packet afterwards, to avoid having to do an expensive lookup of the station from the packet data on every packet. This patch does *not* include any mechanism to wake a throttled TXQ again, on the assumption that this will happen anyway as a side effect of whatever freed the skb (most commonly a TX completion). Signed-off-by: Toke Høiland-Jørgensen Link: https://lore.kernel.org/r/20191119060610.76681-5-kyan@google.com Signed-off-by: Johannes Berg --- --- a/include/net/mac80211.h +++ b/include/net/mac80211.h @@ -1060,6 +1060,22 @@ struct ieee80211_tx_info { }; }; +static inline u16 +ieee80211_info_set_tx_time_est(struct ieee80211_tx_info *info, u16 tx_time_est) +{ + /* We only have 10 bits in tx_time_est, so store airtime + * in increments of 4us and clamp the maximum to 2**12-1 + */ + info->tx_time_est = min_t(u16, tx_time_est, 4095) >> 2; + return info->tx_time_est << 2; +} + +static inline u16 +ieee80211_info_get_tx_time_est(struct ieee80211_tx_info *info) +{ + return info->tx_time_est << 2; +} + /** * struct ieee80211_tx_status - extended tx staus info for rate control * --- a/net/mac80211/status.c +++ b/net/mac80211/status.c @@ -670,12 +670,26 @@ static void ieee80211_report_used_skb(st struct sk_buff *skb, bool dropped) { struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb); + u16 tx_time_est = ieee80211_info_get_tx_time_est(info); struct ieee80211_hdr *hdr = (void *)skb->data; bool acked = info->flags & IEEE80211_TX_STAT_ACK; if (dropped) acked = false; + if (tx_time_est) { + struct sta_info *sta; + + rcu_read_lock(); + + sta = sta_info_get_by_addrs(local, hdr->addr1, hdr->addr2); + ieee80211_sta_update_pending_airtime(local, sta, + skb_get_queue_mapping(skb), + tx_time_est, + true); + rcu_read_unlock(); + } + if (info->flags & IEEE80211_TX_INTFL_MLME_CONN_TX) { struct ieee80211_sub_if_data *sdata; @@ -885,6 +899,7 @@ static void __ieee80211_tx_status(struct struct ieee80211_bar *bar; int shift = 0; int tid = IEEE80211_NUM_TIDS; + u16 tx_time_est; rates_idx = ieee80211_tx_get_rates(hw, info, &retry_count); @@ -996,6 +1011,17 @@ static void __ieee80211_tx_status(struct ieee80211_sta_register_airtime(&sta->sta, tid, info->status.tx_time, 0); + if ((tx_time_est = ieee80211_info_get_tx_time_est(info)) > 0) { + /* Do this here to avoid the expensive lookup of the sta + * in ieee80211_report_used_skb(). + */ + ieee80211_sta_update_pending_airtime(local, sta, + skb_get_queue_mapping(skb), + tx_time_est, + true); + ieee80211_info_set_tx_time_est(info, 0); + } + if (ieee80211_hw_check(&local->hw, REPORTS_TX_ACK_STATUS)) { if (acked) { if (sta->status_stats.lost_packets) --- a/net/mac80211/tx.c +++ b/net/mac80211/tx.c @@ -3544,6 +3544,9 @@ struct sk_buff *ieee80211_tx_dequeue(str WARN_ON_ONCE(softirq_count() == 0); + if (!ieee80211_txq_airtime_check(hw, txq)) + return NULL; + begin: spin_lock_bh(&fq->lock); @@ -3654,6 +3657,21 @@ begin: } IEEE80211_SKB_CB(skb)->control.vif = vif; + + if (local->airtime_flags & AIRTIME_USE_AQL) { + u32 airtime; + + airtime = ieee80211_calc_expected_tx_airtime(hw, vif, txq->sta, + skb->len); + if (airtime) { + airtime = ieee80211_info_set_tx_time_est(info, airtime); + ieee80211_sta_update_pending_airtime(local, tx.sta, + txq->ac, + airtime, + false); + } + } + return skb; out: