Lustre 1.6 Operations Manual

21.2 LNET Tunables
This section describes LNET tunables.
21.2.0.1 Transmit and receive buffer size:
With Lustre release 1.4.7 and later, ksocklnd now has separate parameters for the
transmit and receive buffers.
options ksocklnd tx_buffer_size=0 rx_buffer_size=0
If these parameters are left at the default value (0), the system automatically tunes
the transmit and receive buffer size. In almost every case, this default produces the
best performance. Do not attempt to tune these parameters unless you are a network
expert.
21.2.0.2 enable_irq_affinity
By default, this parameter is OFF. In the normal case on an SMP system, we would
like network traffic to remain local to a single CPU. This helps to keep the processor
cache warm, and minimizes the impact of context switches. This is especially helpful
when an SMP system has more than one network interface, and ideal when the
number of interfaces equals the number of CPUs.
If you have an SMP platform with a single fast interface such as 10 GB Ethernet and
more than 2 CPUs, you may see improved performance by turning this parameter to
OFF. You should, as always, test to compare the performance impact.
Chapter 21 Lustre Tuning 21-3