igb: Improve multiqueue AIM support

Improve multiqueue performance
Change itr_val to reflect ITR timer value instead of ints/sec
Cleaned up AIM algorithms in general

Based on work by Mitch Williams
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by: Mitch Williams <mitch.a.williams@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/net/igb/igb.h

@@ -47,7 +47,9 @@ struct igb_adapter;
 
 #define IGB_MIN_DYN_ITR 3000
 #define IGB_MAX_DYN_ITR 96000
-#define IGB_START_ITR 6000
+
+/* ((1000000000ns / (6000ints/s * 1024ns)) << 2 = 648 */
+#define IGB_START_ITR 648
 
 #define IGB_DYN_ITR_PACKET_THRESHOLD 2
 #define IGB_DYN_ITR_LENGTH_LOW 200
@@ -170,9 +172,10 @@ struct igb_ring {
 		};
 		/* RX */
 		struct {
-			int no_itr_adjust;
 			struct igb_queue_stats rx_stats;
 			struct napi_struct napi;
+			int set_itr;
+			struct igb_ring *buddy;
 #ifdef CONFIG_IGB_LRO
 			struct net_lro_mgr lro_mgr;
 			bool lro_used;
@@ -219,7 +222,6 @@ struct igb_adapter {
 	u32 itr_setting;
 	u16 tx_itr;
 	u16 rx_itr;
-	int set_itr;
 
 	struct work_struct reset_task;
 	struct work_struct watchdog_task;

drivers/net/igb/igb_ethtool.c

@@ -1861,6 +1861,8 @@ static int igb_set_coalesce(struct net_device *netdev,
 			    struct ethtool_coalesce *ec)
 {
 	struct igb_adapter *adapter = netdev_priv(netdev);
+	struct e1000_hw *hw = &adapter->hw;
+	int i;
 
 	if ((ec->rx_coalesce_usecs > IGB_MAX_ITR_USECS) ||
 	    ((ec->rx_coalesce_usecs > 3) &&
@@ -1869,13 +1871,16 @@ static int igb_set_coalesce(struct net_device *netdev,
 		return -EINVAL;
 
 	/* convert to rate of irq's per second */
-	if (ec->rx_coalesce_usecs <= 3)
+	if (ec->rx_coalesce_usecs && ec->rx_coalesce_usecs <= 3) {
 		adapter->itr_setting = ec->rx_coalesce_usecs;
-	else
-		adapter->itr_setting = (1000000 / ec->rx_coalesce_usecs);
+		adapter->itr = IGB_START_ITR;
+	} else {
+		adapter->itr_setting = ec->rx_coalesce_usecs << 2;
+		adapter->itr = adapter->itr_setting;
+	}
 
-	if (netif_running(netdev))
-		igb_reinit_locked(adapter);
+	for (i = 0; i < adapter->num_rx_queues; i++)
+		wr32(adapter->rx_ring[i].itr_register, adapter->itr);
 
 	return 0;
 }
@@ -1888,7 +1893,7 @@ static int igb_get_coalesce(struct net_device *netdev,
 	if (adapter->itr_setting <= 3)
 		ec->rx_coalesce_usecs = adapter->itr_setting;
 	else
-		ec->rx_coalesce_usecs = 1000000 / adapter->itr_setting;
+		ec->rx_coalesce_usecs = adapter->itr_setting >> 2;
 
 	return 0;
 }