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

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This fix a performance bug introduced by commit 90b1ebe "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>

...

This commit is contained in:

Ido Shamay 2014-02-21 12:39:18 +02:00 • committed by David S. Miller

parent 0251248232

commit bb2146bc88

2 changed files with 5 additions and 3 deletions

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5

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

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3

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

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