On 09.04.2013 14:49, Hal Rosenstock wrote: > On 4/9/2013 7:12 AM, Vasiliy Tolstov wrote: >> Hello. I have some servers, with mellanox ConnectX-3 and have some questions: >> Why max_mtu differs with active_mtu? > > What does peer port say for max MTU ? > >> How can i set active mtu? > > SM sets active MTU to min of peer ports max MTUs.
So with "peer port max MTU" do you mean this file?: /sys/class/infiniband/mlx4_0/device/mlx4_port1_mtu I've seen that it can be set as well. I've got two ConnectX-2 machines connected back2back. In general these have 4K max and active. So let's try something: Host1: $ echo 2048 > /sys/class/infiniband/mlx4_0/device/mlx4_port1_mtu # Port is not active, let's reactivate it. $ echo 1 > /sys/class/infiniband/mlx4_0/device/enable ibv_devinfo Host1: max_mtu: 2048 (4) active_mtu: 2048 (4) Host2: max_mtu: 4096 (5) active_mtu: 2048 (4) Both had "4096 (5)" before everywhere. So that's the recommended way to reduce the MTU? I've heard that reducing the MTU in a fabric can help fighting congestion issues. As congestion control doesn't work yet, could this help against congestion? Cheers, Sebastian -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
