A quick tip for optimizing TCP performance on linux.

edit /etc/sysctl.conf add the lines:

If using gigabit ethernet:

net.ipv4.tcp_mem= 98304 131072 196608
net.ipv4.tcp_window_scaling=1
net.core.wmem_default = 65536
net.core.rmem_default = 65536
net.core.wmem_max=8388608

To reload these use:

# sysctl -p

If using infiniband:

net.ipv4.tcp_window_scaling=1
net.ipv4.tcp_timestamps=0
net.ipv4.tcp_sack=0
net.ipv4.tcp_rmem=10000000 10000000 10000000
net.ipv4.tcp_wmem=10000000 10000000 10000000
net.ipv4.tcp_mem=10000000 10000000 10000000
net.core.rmem_max=524287
net.core.wmem_max=524287
net.core.rmem_default=524287
net.core.wmem_default=524287
net.core.optmem_max=524287
net.core.netdev_max_backlog=300000