Q-Logic OFED, IB0056101-00 G.02 manual Other Configuration Changing the MTU Size

Configuring Drivers and Services

Other Configuration: Changing the MTU Size

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2.Check that you have a /etc/dat.conf file. It should be installed by the dapl- RPM. The file dat.conf contains a list of interface adapters supported by uDAPL service providers. In particular, it must contain mapping entries for OpenIB-cma for dapl 1.2.x, in a form similar to this (all on one line):

OpenIB-cma u1.2 nonthreadsafe default libdaplcma.so.1 dapl.1.2 "ib0 0" ""

3.On every node, type the following command (as root):

# modprobe rdma_ucm

To ensure that the module is loaded whenever the driver is loaded, add RDMA_UCM_LOAD=yes to the /etc/infiniband/openib.conf file. (Note that rdma_cm is also used, but it is loaded automatically.)

4.Bring up an IPoIB interface on every node, eg. ib0. See the instructions for configuring IPoIB for more details.

For more information on using Intel MPI, see the “Using Other MPIs” section in the QLogic HCA and QLogic OFED Software Users Guide.

Other Configuration: Changing the MTU Size

The Maximum Transfer Unit (MTU) is set to 4K and enabled in the driver by default. To change the driver default back to 2K MTU, add this line (as root) in

/etc/modprobe.conf (or in /etc/modprobe.conf.local on SLES):

options ib ipath mtu4096=0

Restart the driver as described in “Managing the InfiniPath Driver” on page 6-15.

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