net/mlx4: Fix limiting number of IRQ's instead of RSS queues

This fix a performance bug introduced by commit 90b1ebe7 "mlx4: set
maximal number of default RSS queues", which limits the numbers of IRQs
opened by core module.
The limit should be on the number of queues in the indirection table -
rx_rings, and not on the number of IRQ's. Also, limiting on mlx4_core
initialization instead of in mlx4_en, prevented using "ethtool -L" to
utilize all the CPU's, when performance mode is prefered, since limiting
this number to 8 reduces overall packet rate by 15%-50% in multiple TCP
streams applications.

For example, after running ethtool -L <ethx> rx 16

          Packet rate
Before the fix  897799
After the fix   1142070

Results were obtained using netperf:

S=200 ; ( for i in $(seq 1 $S) ; do ( \
  netperf -H 11.7.13.55 -t TCP_RR -l 30 &) ; \
  wait ; done | grep "1        1" | awk '{SUM+=$6} END {print SUM}' )

CC: Yuval Mintz <yuvalmin@broadcom.com>
Signed-off-by: Ido Shamay <idos@mellanox.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx4/en_rx.c

@@ -322,6 +322,7 @@ void mlx4_en_set_num_rx_rings(struct mlx4_en_dev *mdev)
 {
 	int i;
 	int num_of_eqs;
+	int num_rx_rings;
 	struct mlx4_dev *dev = mdev->dev;
 
 	mlx4_foreach_port(i, dev, MLX4_PORT_TYPE_ETH) {
@@ -335,8 +336,10 @@ void mlx4_en_set_num_rx_rings(struct mlx4_en_dev *mdev)
 					   dev->caps.comp_pool/
 					   dev->caps.num_ports) - 1;
 
+		num_rx_rings = min_t(int, num_of_eqs,
+				     netif_get_num_default_rss_queues());
 		mdev->profile.prof[i].rx_ring_num =
-			rounddown_pow_of_two(num_of_eqs);
+			rounddown_pow_of_two(num_rx_rings);
 	}
 }
 

drivers/net/ethernet/mellanox/mlx4/main.c

@@ -41,7 +41,6 @@
 #include <linux/slab.h>
 #include <linux/io-mapping.h>
 #include <linux/delay.h>
-#include <linux/netdevice.h>
 #include <linux/kmod.h>
 
 #include <linux/mlx4/device.h>
@@ -1974,7 +1973,7 @@ static void mlx4_enable_msi_x(struct mlx4_dev *dev)
 	struct mlx4_priv *priv = mlx4_priv(dev);
 	struct msix_entry *entries;
 	int nreq = min_t(int, dev->caps.num_ports *
-			 min_t(int, netif_get_num_default_rss_queues() + 1,
+			 min_t(int, num_online_cpus() + 1,
 			       MAX_MSIX_P_PORT) + MSIX_LEGACY_SZ, MAX_MSIX);
 	int i;