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6d49a25804
This reverts the airtime scheduler back from the virtual-time based scheduler to the deficit round robin scheduler implementation. This reduces burstiness and improves fairness by improving interaction with AQL. Signed-off-by: Felix Fietkau <nbd@nbd.name>
132 lines
4.0 KiB
Diff
132 lines
4.0 KiB
Diff
From: Felix Fietkau <nbd@nbd.name>
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Date: Mon, 20 Jun 2022 21:26:34 +0200
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Subject: [PATCH] mac80211: add a per-PHY AQL limit to improve fairness
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In order to maintain fairness, the amount of queueing needs to be limited
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beyond the simple per-station AQL budget, otherwise the driver can simply
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repeatedly do scheduling rounds until all queues that have not used their
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AQL budget become eligble.
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To be conservative, use the high AQL limit for the first txq and add half
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of the low AQL for each subsequent queue.
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Signed-off-by: Felix Fietkau <nbd@nbd.name>
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---
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--- a/net/mac80211/ieee80211_i.h
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+++ b/net/mac80211/ieee80211_i.h
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@@ -1211,6 +1211,7 @@ struct ieee80211_local {
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u32 aql_txq_limit_high[IEEE80211_NUM_ACS];
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u32 aql_threshold;
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atomic_t aql_total_pending_airtime;
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+ atomic_t aql_ac_pending_airtime[IEEE80211_NUM_ACS];
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const struct ieee80211_ops *ops;
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--- a/net/mac80211/main.c
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+++ b/net/mac80211/main.c
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@@ -712,6 +712,7 @@ struct ieee80211_hw *ieee80211_alloc_hw_
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local->aql_txq_limit_low[i] = IEEE80211_DEFAULT_AQL_TXQ_LIMIT_L;
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local->aql_txq_limit_high[i] =
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IEEE80211_DEFAULT_AQL_TXQ_LIMIT_H;
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+ atomic_set(&local->aql_ac_pending_airtime[i], 0);
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}
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local->airtime_flags = AIRTIME_USE_TX | AIRTIME_USE_RX;
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--- a/net/mac80211/sta_info.c
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+++ b/net/mac80211/sta_info.c
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@@ -1929,6 +1929,7 @@ void ieee80211_sta_update_pending_airtim
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&sta->airtime[ac].aql_tx_pending);
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atomic_add(tx_airtime, &local->aql_total_pending_airtime);
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+ atomic_add(tx_airtime, &local->aql_ac_pending_airtime[ac]);
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return;
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}
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@@ -1940,14 +1941,17 @@ void ieee80211_sta_update_pending_airtim
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tx_pending, 0);
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}
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+ atomic_sub(tx_airtime, &local->aql_total_pending_airtime);
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tx_pending = atomic_sub_return(tx_airtime,
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- &local->aql_total_pending_airtime);
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+ &local->aql_ac_pending_airtime[ac]);
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if (WARN_ONCE(tx_pending < 0,
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"Device %s AC %d pending airtime underflow: %u, %u",
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wiphy_name(local->hw.wiphy), ac, tx_pending,
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- tx_airtime))
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- atomic_cmpxchg(&local->aql_total_pending_airtime,
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+ tx_airtime)) {
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+ atomic_cmpxchg(&local->aql_ac_pending_airtime[ac],
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tx_pending, 0);
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+ atomic_sub(tx_pending, &local->aql_total_pending_airtime);
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+ }
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}
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int sta_info_move_state(struct sta_info *sta,
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--- a/net/mac80211/tx.c
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+++ b/net/mac80211/tx.c
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@@ -3863,6 +3863,9 @@ struct ieee80211_txq *ieee80211_next_txq
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spin_lock_bh(&local->active_txq_lock[ac]);
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+ if (!local->schedule_round[ac])
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+ goto out;
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+
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begin:
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txqi = list_first_entry_or_null(&local->active_txqs[ac],
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struct txq_info,
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@@ -3984,6 +3987,25 @@ bool ieee80211_txq_airtime_check(struct
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}
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EXPORT_SYMBOL(ieee80211_txq_airtime_check);
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+static bool
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+ieee80211_txq_schedule_airtime_check(struct ieee80211_local *local, u8 ac)
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+{
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+ unsigned int num_txq = 0;
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+ struct txq_info *txq;
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+ u32 aql_limit;
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+
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+ if (!wiphy_ext_feature_isset(local->hw.wiphy, NL80211_EXT_FEATURE_AQL))
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+ return true;
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+
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+ list_for_each_entry(txq, &local->active_txqs[ac], schedule_order)
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+ num_txq++;
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+
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+ aql_limit = (num_txq - 1) * local->aql_txq_limit_low[ac] / 2 +
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+ local->aql_txq_limit_high[ac];
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+
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+ return atomic_read(&local->aql_ac_pending_airtime[ac]) < aql_limit;
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+}
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+
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bool ieee80211_txq_may_transmit(struct ieee80211_hw *hw,
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struct ieee80211_txq *txq)
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{
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@@ -4000,6 +4022,9 @@ bool ieee80211_txq_may_transmit(struct i
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if (list_empty(&txqi->schedule_order))
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goto out;
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+ if (!ieee80211_txq_schedule_airtime_check(local, ac))
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+ goto out;
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+
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list_for_each_entry_safe(iter, tmp, &local->active_txqs[ac],
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schedule_order) {
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if (iter == txqi)
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@@ -4039,7 +4064,15 @@ void ieee80211_txq_schedule_start(struct
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struct ieee80211_local *local = hw_to_local(hw);
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spin_lock_bh(&local->active_txq_lock[ac]);
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- local->schedule_round[ac]++;
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+
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+ if (ieee80211_txq_schedule_airtime_check(local, ac)) {
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+ local->schedule_round[ac]++;
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+ if (!local->schedule_round[ac])
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+ local->schedule_round[ac]++;
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+ } else {
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+ local->schedule_round[ac] = 0;
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+ }
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+
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spin_unlock_bh(&local->active_txq_lock[ac]);
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}
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EXPORT_SYMBOL(ieee80211_txq_schedule_start);
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