mac80211: optimize aggregation session timeout handling
Calling mod_timer from the rx/tx hotpath is somewhat expensive, and the
timeout doesn't need to be so precise.
Switch to a different strategy: Schedule the timer initially, store jiffies
of all last rx/tx activity which would previously modify the timer, and
let the timer re-arm itself after checking the last rx/tx timestamp.
Make the session timers deferrable to avoid causing extra wakeups on systems
running on battery.
This visibly reduces CPU load under high network load on small embedded
systems.
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/agg-tx.c b/net/mac80211/agg-tx.c
index 76be6174..9628a18 100644
--- a/net/mac80211/agg-tx.c
+++ b/net/mac80211/agg-tx.c
@@ -417,6 +417,18 @@
u8 *timer_to_id = ptid - *ptid;
struct sta_info *sta = container_of(timer_to_id, struct sta_info,
timer_to_tid[0]);
+ struct tid_ampdu_tx *tid_tx;
+ unsigned long timeout;
+
+ tid_tx = rcu_dereference_protected_tid_tx(sta, *ptid);
+ if (!tid_tx)
+ return;
+
+ timeout = tid_tx->last_tx + TU_TO_JIFFIES(tid_tx->timeout);
+ if (time_is_after_jiffies(timeout)) {
+ mod_timer(&tid_tx->session_timer, timeout);
+ return;
+ }
#ifdef CONFIG_MAC80211_HT_DEBUG
printk(KERN_DEBUG "tx session timer expired on tid %d\n", (u16)*ptid);
@@ -542,7 +554,7 @@
/* tx timer */
tid_tx->session_timer.function = sta_tx_agg_session_timer_expired;
tid_tx->session_timer.data = (unsigned long)&sta->timer_to_tid[tid];
- init_timer(&tid_tx->session_timer);
+ init_timer_deferrable(&tid_tx->session_timer);
/* assign a dialog token */
sta->ampdu_mlme.dialog_token_allocator++;
@@ -884,9 +896,11 @@
sta->ampdu_mlme.addba_req_num[tid] = 0;
- if (tid_tx->timeout)
+ if (tid_tx->timeout) {
mod_timer(&tid_tx->session_timer,
TU_TO_EXP_TIME(tid_tx->timeout));
+ tid_tx->last_tx = jiffies;
+ }
} else {
___ieee80211_stop_tx_ba_session(sta, tid, WLAN_BACK_INITIATOR,