HP-MPI User's Guide (11th Edition)

Tuning
Tunable parameters
Chapter 5 183
Tunable parameters
HP-MPI provides a mix of command line options and environment
variables that can be used to influence the behavior, and thus the
performance of the library. The full list of command line options and
environment variables are presented in the sections “mpirun options”
and “Runtime environment variables” of Chapter 3. The options and
variables of interest to performance tuning include the following:
MPI_FLAGS=y
This option can be used to control the behavior of the HP-MPI library
when waiting for an event to occur, such as the arrival of a message. See
“MPI_FLAGS” on page 137 for more information.
MPI_TCP_CORECVLIMIT
Setting this variable to a larger value can allow HP-MPI to utilize more
parallelism during its low-level message transfers, but can greatly
reduce performance by causing switch congestion. See
“MPI_TCP_CORECVLIMIT” on page 160 for more information.
MPI_SOCKBUFSIZE
Increasing this value has shown performance gains for some applications
running on TCP networks. See “MPI_SOCKBUFSIZE” on page 160 for
more information.
-cpu_bind, MPI_BIND_MAP, MPI_CPU_AFFINITY,
MPI_CPU_SPIN
The -cpu_bind command line option and associated environment
variables can improve the performance of many applications by binding a
process to a particular CPU. See “mpirun options” on page 119, “CPU
Bind environment variables” on page 144, and “Binding ranks to ldoms
(-cpu_bind)” on page 190 for more information.