mlx4_en: Coalescing target is equal for all mtu's

The interrupt moderation should not depend on number of incoming
bytes, but on number of incoming packets.
The previous scheme caused very high interrupts rate for small
messages when big MTU was configured.

Signed-off-by: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/mlx4/en_ethtool.c

@@ -268,8 +268,7 @@ static int mlx4_en_set_coalesce(struct net_device *dev,
 
 	priv->rx_frames = (coal->rx_max_coalesced_frames ==
 			   MLX4_EN_AUTO_CONF) ?
-				MLX4_EN_RX_COAL_TARGET /
-				priv->dev->mtu + 1 :
+				MLX4_EN_RX_COAL_TARGET :
 				coal->rx_max_coalesced_frames;
 	priv->rx_usecs = (coal->rx_coalesce_usecs ==
 			  MLX4_EN_AUTO_CONF) ?

drivers/net/mlx4/en_netdev.c

@@ -372,7 +372,7 @@ static void mlx4_en_set_default_moderation(struct mlx4_en_priv *priv)
 	 *   satisfy our coelsing target.
 	 * - moder_time is set to a fixed value.
 	 */
-	priv->rx_frames = MLX4_EN_RX_COAL_TARGET / priv->dev->mtu + 1;
+	priv->rx_frames = MLX4_EN_RX_COAL_TARGET;
 	priv->rx_usecs = MLX4_EN_RX_COAL_TIME;
 	en_dbg(INTR, priv, "Default coalesing params for mtu:%d - "
 			   "rx_frames:%d rx_usecs:%d\n",

drivers/net/mlx4/mlx4_en.h

@@ -143,8 +143,8 @@ enum {
 #define MLX4_EN_DEF_TX_RING_SIZE	1024
 #define MLX4_EN_DEF_RX_RING_SIZE  	1024
 
-/* Target number of bytes to coalesce with interrupt moderation */
-#define MLX4_EN_RX_COAL_TARGET	0x20000
+/* Target number of packets to coalesce with interrupt moderation */
+#define MLX4_EN_RX_COAL_TARGET	44
 #define MLX4_EN_RX_COAL_TIME	0x10
 
 #define MLX4_EN_TX_COAL_PKTS	5