e1000: implement more efficient tx queue locking

Implement more efficient locking (avoid the lock) when checking for
a stopped queue.  Also don't wake the queue unless the threshold is
reached to avoid queue on/off thrash.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com>
Signed-off-by: John Ronciak <john.ronciak@intel.com>

diff --git a/drivers/net/e1000/e1000_main.c b/drivers/net/e1000/e1000_main.c
index f604a1dea399de77c697b8ffc6aef71b04837a61..3c37c40339fbf9fab2031a9479bc1a19362a731d 100644 (file)
--- a/drivers/net/e1000/e1000_main.c
+++ b/drivers/net/e1000/e1000_main.c
@@ -3400,13 +3400,15 @@ e1000_clean_tx_irq(struct e1000_adapter *adapter,
 
        tx_ring->next_to_clean = i;
 
-       spin_lock(&tx_ring->tx_lock);
-
+#define TX_WAKE_THRESHOLD 32
        if (unlikely(cleaned && netif_queue_stopped(netdev) &&
-                   netif_carrier_ok(netdev)))
-               netif_wake_queue(netdev);
-
-       spin_unlock(&tx_ring->tx_lock);
+                    netif_carrier_ok(netdev))) {
+               spin_lock(&tx_ring->tx_lock);
+               if (netif_queue_stopped(netdev) &&
+                   (E1000_DESC_UNUSED(tx_ring) >= TX_WAKE_THRESHOLD))
+                       netif_wake_queue(netdev);
+               spin_unlock(&tx_ring->tx_lock);
+       }
 
        if (adapter->detect_tx_hung) {
                /* Detect a transmit hang in hardware, this serializes the