ar9170: improve network latency

AR9170 has the bad habit of choking when traffic builds up.
Tests have shown that this can partially be attributed to
a huge buildup of backlogged frames.

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --git a/drivers/net/wireless/ath/ar9170/ar9170.h b/drivers/net/wireless/ath/ar9170/ar9170.h
index d95a7d4..44c54b8 100644 (file)
--- a/drivers/net/wireless/ath/ar9170/ar9170.h
+++ b/drivers/net/wireless/ath/ar9170/ar9170.h
@@ -152,6 +152,8 @@ struct ar9170_sta_tid {
 
 #define AR9170_NUM_TX_STATUS           128
 #define AR9170_NUM_TX_AGG_MAX          30
+#define AR9170_NUM_TX_LIMIT_HARD       AR9170_TXQ_DEPTH
+#define AR9170_NUM_TX_LIMIT_SOFT       (AR9170_TXQ_DEPTH - 10)
 
 struct ar9170 {
        struct ieee80211_hw *hw;

diff --git a/drivers/net/wireless/ath/ar9170/main.c b/drivers/net/wireless/ath/ar9170/main.c
index cbf59b1..3cec2f1 100644 (file)
--- a/drivers/net/wireless/ath/ar9170/main.c
+++ b/drivers/net/wireless/ath/ar9170/main.c
@@ -430,7 +430,7 @@ void ar9170_tx_callback(struct ar9170 *ar, struct sk_buff *skb)
        spin_lock_irqsave(&ar->tx_stats_lock, flags);
        ar->tx_stats[queue].len--;
 
-       if (skb_queue_empty(&ar->tx_pending[queue])) {
+       if (ar->tx_stats[queue].len < AR9170_NUM_TX_LIMIT_SOFT) {
 #ifdef AR9170_QUEUE_STOP_DEBUG
                printk(KERN_DEBUG "%s: wake queue %d\n",
                       wiphy_name(ar->hw->wiphy), queue);
@@ -1716,6 +1716,21 @@ static void ar9170_tx(struct ar9170 *ar)
 
        for (i = 0; i < __AR9170_NUM_TXQ; i++) {
                spin_lock_irqsave(&ar->tx_stats_lock, flags);
+               frames = min(ar->tx_stats[i].limit - ar->tx_stats[i].len,
+                            skb_queue_len(&ar->tx_pending[i]));
+
+               if (remaining_space < frames) {
+#ifdef AR9170_QUEUE_DEBUG
+                       printk(KERN_DEBUG "%s: tx quota reached queue:%d, "
+                              "remaining slots:%d, needed:%d\n",
+                              wiphy_name(ar->hw->wiphy), i, remaining_space,
+                              frames);
+#endif /* AR9170_QUEUE_DEBUG */
+                       frames = remaining_space;
+               }
+
+               ar->tx_stats[i].len += frames;
+               ar->tx_stats[i].count += frames;
                if (ar->tx_stats[i].len >= ar->tx_stats[i].limit) {
 #ifdef AR9170_QUEUE_DEBUG
                        printk(KERN_DEBUG "%s: queue %d full\n",
@@ -1733,25 +1748,8 @@ static void ar9170_tx(struct ar9170 *ar)
                        __ar9170_dump_txstats(ar);
 #endif /* AR9170_QUEUE_STOP_DEBUG */
                        ieee80211_stop_queue(ar->hw, i);
-                       spin_unlock_irqrestore(&ar->tx_stats_lock, flags);
-                       continue;
-               }
-
-               frames = min(ar->tx_stats[i].limit - ar->tx_stats[i].len,
-                            skb_queue_len(&ar->tx_pending[i]));
-
-               if (remaining_space < frames) {
-#ifdef AR9170_QUEUE_DEBUG
-                       printk(KERN_DEBUG "%s: tx quota reached queue:%d, "
-                              "remaining slots:%d, needed:%d\n",
-                              wiphy_name(ar->hw->wiphy), i, remaining_space,
-                              frames);
-#endif /* AR9170_QUEUE_DEBUG */
-                       frames = remaining_space;
                }
 
-               ar->tx_stats[i].len += frames;
-               ar->tx_stats[i].count += frames;
                spin_unlock_irqrestore(&ar->tx_stats_lock, flags);
 
                if (!frames)