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-rx.c b/net/mac80211/agg-rx.c
index 64d3ce5..a070d4f 100644
--- a/net/mac80211/agg-rx.c
+++ b/net/mac80211/agg-rx.c
@@ -142,6 +142,18 @@
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_rx *tid_rx;
+ unsigned long timeout;
+
+ tid_rx = rcu_dereference(sta->ampdu_mlme.tid_rx[*ptid]);
+ if (!tid_rx)
+ return;
+
+ timeout = tid_rx->last_rx + TU_TO_JIFFIES(tid_rx->timeout);
+ if (time_is_after_jiffies(timeout)) {
+ mod_timer(&tid_rx->session_timer, timeout);
+ return;
+ }
#ifdef CONFIG_MAC80211_HT_DEBUG
printk(KERN_DEBUG "rx session timer expired on tid %d\n", (u16)*ptid);
@@ -291,7 +303,7 @@
/* rx timer */
tid_agg_rx->session_timer.function = sta_rx_agg_session_timer_expired;
tid_agg_rx->session_timer.data = (unsigned long)&sta->timer_to_tid[tid];
- init_timer(&tid_agg_rx->session_timer);
+ init_timer_deferrable(&tid_agg_rx->session_timer);
/* rx reorder timer */
tid_agg_rx->reorder_timer.function = sta_rx_agg_reorder_timer_expired;
@@ -335,8 +347,10 @@
/* activate it for RX */
rcu_assign_pointer(sta->ampdu_mlme.tid_rx[tid], tid_agg_rx);
- if (timeout)
+ if (timeout) {
mod_timer(&tid_agg_rx->session_timer, TU_TO_EXP_TIME(timeout));
+ tid_agg_rx->last_rx = jiffies;
+ }
end:
mutex_unlock(&sta->ampdu_mlme.mtx);