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Commit 12d3952f authored by Felix Fietkau's avatar Felix Fietkau Committed by John W. Linville
Browse files

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: default avatarFelix Fietkau <nbd@openwrt.org>
Signed-off-by: default avatarJohn W. Linville <linville@tuxdriver.com>
parent fcb2c9e1

net/mac80211/agg-rx.c

+16 −2
Original line number Diff line number Diff line
@@ -142,6 +142,18 @@ static void sta_rx_agg_session_timer_expired(unsigned long data) 
	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 @@ void ieee80211_process_addba_request(struct ieee80211_local *local, 
	/* 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 @@ void ieee80211_process_addba_request(struct ieee80211_local *local, 
	/* 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);

net/mac80211/agg-tx.c

+16 −2
Original line number Diff line number Diff line
@@ -417,6 +417,18 @@ static void sta_tx_agg_session_timer_expired(unsigned long data) 
	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 @@ int ieee80211_start_tx_ba_session(struct ieee80211_sta *pubsta, u16 tid, 
	/* 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 @@ void ieee80211_process_addba_resp(struct ieee80211_local *local, 


		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,

net/mac80211/ieee80211_i.h

+2 −1
Original line number Diff line number Diff line
@@ -52,7 +52,8 @@ struct ieee80211_local; 
 * increased memory use (about 2 kB of RAM per entry). */

#define IEEE80211_FRAGMENT_MAX 4



#define TU_TO_EXP_TIME(x)	(jiffies + usecs_to_jiffies((x) * 1024))

#define TU_TO_JIFFIES(x)	(usecs_to_jiffies((x) * 1024))

#define TU_TO_EXP_TIME(x)	(jiffies + TU_TO_JIFFIES(x))



#define IEEE80211_DEFAULT_UAPSD_QUEUES \

	(IEEE80211_WMM_IE_STA_QOSINFO_AC_BK |	\

net/mac80211/rx.c

+1 −2
Original line number Diff line number Diff line
@@ -793,8 +793,7 @@ static void ieee80211_rx_reorder_ampdu(struct ieee80211_rx_data *rx) 


	/* reset session timer */

	if (tid_agg_rx->timeout)

		mod_timer(&tid_agg_rx->session_timer,

			  TU_TO_EXP_TIME(tid_agg_rx->timeout));

		tid_agg_rx->last_rx = jiffies;



	/* if this mpdu is fragmented - terminate rx aggregation session */

	sc = le16_to_cpu(hdr->seq_ctrl);

net/mac80211/sta_info.h

+4 −0
Original line number Diff line number Diff line
@@ -101,6 +101,7 @@ enum ieee80211_sta_info_flags { 
 * @dialog_token: dialog token for aggregation session

 * @timeout: session timeout value to be filled in ADDBA requests

 * @state: session state (see above)

 * @last_tx: jiffies of last tx activity

 * @stop_initiator: initiator of a session stop

 * @tx_stop: TX DelBA frame when stopping

 * @buf_size: reorder buffer size at receiver
@@ -122,6 +123,7 @@ struct tid_ampdu_tx { 
	struct timer_list addba_resp_timer;

	struct sk_buff_head pending;

	unsigned long state;

	unsigned long last_tx;

	u16 timeout;

	u8 dialog_token;

	u8 stop_initiator;
@@ -139,6 +141,7 @@ struct tid_ampdu_tx { 
 * @reorder_time: jiffies when skb was added

 * @session_timer: check if peer keeps Tx-ing on the TID (by timeout value)

 * @reorder_timer: releases expired frames from the reorder buffer.

 * @last_rx: jiffies of last rx activity

 * @head_seq_num: head sequence number in reordering buffer.

 * @stored_mpdu_num: number of MPDUs in reordering buffer

 * @ssn: Starting Sequence Number expected to be aggregated.
@@ -163,6 +166,7 @@ struct tid_ampdu_rx { 
	unsigned long *reorder_time;

	struct timer_list session_timer;

	struct timer_list reorder_timer;

	unsigned long last_rx;

	u16 head_seq_num;

	u16 stored_mpdu_num;

	u16 ssn;