2020-07-24 18:29:14

by Felix Fietkau

Subject: [PATCH] mac80211: improve AQL tx airtime estimation

AQL does not take into account that most HT/VHT/HE traffic is A-MPDU aggregated.
Because of that, the per-packet airtime overhead is vastly overestimated.
Improve it by assuming an average aggregation length of 16 for non-legacy
traffic if not using the VO AC queue.
This should improve performance with high data rates, especially with multiple
stations

Signed-off-by: Felix Fietkau <[email protected]>
---
net/mac80211/airtime.c | 26 +++++++++++++++++++++-----
net/mac80211/ieee80211_i.h | 2 +-
net/mac80211/tx.c | 3 ++-
3 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/net/mac80211/airtime.c b/net/mac80211/airtime.c
index 9fc2968856c0..366f76c9003d 100644
--- a/net/mac80211/airtime.c
+++ b/net/mac80211/airtime.c
@@ -551,7 +551,7 @@ EXPORT_SYMBOL_GPL(ieee80211_calc_tx_airtime);
u32 ieee80211_calc_expected_tx_airtime(struct ieee80211_hw *hw,
struct ieee80211_vif *vif,
struct ieee80211_sta *pubsta,
- int len)
+ int len, bool ampdu)
{
struct ieee80211_supported_band *sband;
struct ieee80211_chanctx_conf *conf;
@@ -572,10 +572,26 @@ u32 ieee80211_calc_expected_tx_airtime(struct ieee80211_hw *hw,
if (pubsta) {
struct sta_info *sta = container_of(pubsta, struct sta_info,
sta);
-
- return ieee80211_calc_tx_airtime_rate(hw,
- &sta->tx_stats.last_rate,
- band, len);
+ struct ieee80211_tx_rate *rate = &sta->tx_stats.last_rate;
+ u32 airtime;
+
+ if (!(rate->flags & (IEEE80211_TX_RC_VHT_MCS |
+ IEEE80211_TX_RC_MCS)))
+ ampdu = false;
+
+ /*
+ * Assume that HT/VHT transmission on any AC except VO will
+ * use aggregation. Since we don't have reliable reporting
+ * of aggregation length, assume an average of 16.
+ * This will not be very accurate, but much better than simply
+ * assuming un-aggregated tx.
+ */
+ airtime = ieee80211_calc_tx_airtime_rate(hw, rate, band,
+ ampdu ? len * 16 : len);
+ if (ampdu)
+ airtime /= 16;
+
+ return airtime;
}

if (!conf)
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index ec1a71ac65f2..28b154c6e72d 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -2290,7 +2290,7 @@ extern const struct ethtool_ops ieee80211_ethtool_ops;
u32 ieee80211_calc_expected_tx_airtime(struct ieee80211_hw *hw,
struct ieee80211_vif *vif,
struct ieee80211_sta *pubsta,
- int len);
+ int len, bool ampdu);
#ifdef CONFIG_MAC80211_NOINLINE
#define debug_noinline noinline
#else
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 1a2941e5244f..a4e7ef6b0457 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -3721,10 +3721,11 @@ struct sk_buff *ieee80211_tx_dequeue(struct ieee80211_hw *hw,

if (vif &&
wiphy_ext_feature_isset(local->hw.wiphy, NL80211_EXT_FEATURE_AQL)) {
+ bool ampdu = txq->ac != IEEE80211_AC_VO;
u32 airtime;

airtime = ieee80211_calc_expected_tx_airtime(hw, vif, txq->sta,
- skb->len);
+ skb->len, ampdu);
if (airtime) {
airtime = ieee80211_info_set_tx_time_est(info, airtime);
ieee80211_sta_update_pending_airtime(local, tx.sta,
--
2.24.0

2020-08-11 09:29:20

by Toke Høiland-Jørgensen

Subject: Re: [PATCH] mac80211: improve AQL tx airtime estimation

Felix Fietkau <[email protected]> writes:

> AQL does not take into account that most HT/VHT/HE traffic is A-MPDU aggregated.
> Because of that, the per-packet airtime overhead is vastly overestimated.
> Improve it by assuming an average aggregation length of 16 for non-legacy
> traffic if not using the VO AC queue.
> This should improve performance with high data rates, especially with multiple
> stations

This seems reasonable!

Acked-by: Toke Høiland-Jørgensen <[email protected]>