958785508c
- fix ath10k latency issues - reject too large weight values - code cleanup Signed-off-by: Felix Fietkau <nbd@nbd.name>
92 lines
3.8 KiB
Diff
92 lines
3.8 KiB
Diff
From: Felix Fietkau <nbd@nbd.name>
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Date: Sat, 11 Jun 2022 17:28:02 +0200
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Subject: [PATCH] mac80211: fix ieee80211_txq_may_transmit regression
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After switching to the virtual time based airtime scheduler, there were reports
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that ath10k with tx queueing in push-pull mode was experiencing significant
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latency for some stations.
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The reason for it is the fact that queues from which the ath10k firmware wants
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to pull are getting starved by airtime fairness constraints.
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Theoretically the same issue should have been there before the switch to virtual
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time, however it seems that in the old round-robin implementation it was simply
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looping until the requested txq was considered eligible, which led to it pretty
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much ignoring fairness constraints anyway.
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In order to fix the immediate regression, let's make bypassing airtime fairness
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explicit for now.
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Also update the documentation for ieee80211_txq_may_transmit, which was still
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referring to implementation details of the old round-robin scheduler
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Fixes: 2433647bc8d9 ("mac80211: Switch to a virtual time-based airtime scheduler")
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Signed-off-by: Felix Fietkau <nbd@nbd.name>
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---
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--- a/include/net/mac80211.h
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+++ b/include/net/mac80211.h
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@@ -6700,22 +6700,11 @@ void ieee80211_return_txq(struct ieee802
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/**
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* ieee80211_txq_may_transmit - check whether TXQ is allowed to transmit
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*
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- * This function is used to check whether given txq is allowed to transmit by
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- * the airtime scheduler, and can be used by drivers to access the airtime
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- * fairness accounting without going using the scheduling order enfored by
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- * next_txq().
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+ * Returns %true if there is remaining AQL budget for the tx queue and %false
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+ * if it should be throttled. It will also mark the queue as active for the
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+ * airtime scheduler.
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*
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- * Returns %true if the airtime scheduler thinks the TXQ should be allowed to
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- * transmit, and %false if it should be throttled. This function can also have
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- * the side effect of rotating the TXQ in the scheduler rotation, which will
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- * eventually bring the deficit to positive and allow the station to transmit
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- * again.
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- *
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- * The API ieee80211_txq_may_transmit() also ensures that TXQ list will be
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- * aligned against driver's own round-robin scheduler list. i.e it rotates
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- * the TXQ list till it makes the requested node becomes the first entry
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- * in TXQ list. Thus both the TXQ list and driver's list are in sync. If this
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- * function returns %true, the driver is expected to schedule packets
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+ * If this function returns %true, the driver is expected to schedule packets
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* for transmission, and then return the TXQ through ieee80211_return_txq().
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*
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* @hw: pointer as obtained from ieee80211_alloc_hw()
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--- a/net/mac80211/tx.c
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+++ b/net/mac80211/tx.c
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@@ -4100,15 +4100,13 @@ EXPORT_SYMBOL(ieee80211_txq_airtime_chec
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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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- struct txq_info *first_txqi = NULL, *txqi = to_txq_info(txq);
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struct ieee80211_local *local = hw_to_local(hw);
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+ struct txq_info *txqi = to_txq_info(txq);
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struct airtime_sched_info *air_sched;
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struct airtime_info *air_info;
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- struct rb_node *node = NULL;
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bool ret = false;
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u64 now;
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-
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if (!ieee80211_txq_airtime_check(hw, txq))
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return false;
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@@ -4120,19 +4118,6 @@ bool ieee80211_txq_may_transmit(struct i
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now = ktime_get_coarse_boottime_ns();
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- /* Like in ieee80211_next_txq(), make sure the first station in the
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- * scheduling order is eligible for transmission to avoid starvation.
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- */
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- node = rb_first_cached(&air_sched->active_txqs);
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- if (node) {
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- first_txqi = container_of(node, struct txq_info,
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- schedule_order);
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- air_info = to_airtime_info(&first_txqi->txq);
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-
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- if (air_sched->v_t < air_info->v_t)
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- airtime_catchup_v_t(air_sched, air_info->v_t, now);
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- }
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-
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air_info = to_airtime_info(&txqi->txq);
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if (air_info->v_t <= air_sched->v_t) {
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air_sched->last_schedule_activity = now;
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