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ParaStation5 TCP bypass
ParaStation5 Administrator's Guide 21
In order to run applications linked with one of those MPI libraries, ParaStation5 provides dedicated
mpirun commands. The processes for those type of parallel tasks are spawned obeying all restrictions
described in Section 5.3, “Controlling process placement”. Of course, the data transfer will be based
on the communication channels supported by the particular MPI library. For MPIch using ch_p4 (TCP),
ParaStation5 provides an alternative, see Section 5.7, “ParaStation5 TCP bypass”.
The command mpirun-ipath-ps running programs linked with InfiniPath™ MPI is
part of the psipath package. For details how to obtain this package, please contact
<support@par-tec.com>.
For more information refer to mpirun_chp4(8), mpirun_chgm(8), mpirun-ipath-ps(8), mpirun_openib(8) and
mpirun_elan(8).
Using the ParaStation5 command mpiexec, any parallel application supporting the PMI protocol, which is
part of the MPI2 standard, may be run using the ParaStation process environment. Therefore, many other
MPI2 compatible MPI libraries are now supported by ParaStation5.
It is also possible to run serial applications, thus applications not parallelized with MPI, within
ParaStation. ParaStation distinguishes between serial tasks allocating a dedicated CPU within the resource
management system and administrative tasks not allocating a CPU. To execute a serial program, run
mpiexec -n 1 To run an administrative task, use pssh or mpiexec -A -n 1.
For more details on how to start-up serial and parallel jobs refer to mpiexec(8), pssh(8) and the ParaStation5
User's Guide.
5.7. ParaStation5 TCP bypass
ParaStation5 offers a feature called "TCP bypass", enabling applications based on TCP to use the efficient
p4sock protocol. The data will be redirected within the kernel to the p4sock protocol. No modifications to
the application are necessary!
To automatically configure the TCP bypass during ParaStation startup, insert a line like
Env PS_TCP FirstAddress-LastAddress
in the p4sock-section of the configuration file parastation.conf, were FirstAddress and
LastAddress are the first and last IP addresses for which the bypass should be configured.
To enable the bypass for a pair of processes, the library libp4tcp.so, located in the directory /opt/
parastation/lib64 must be pre-loaded by both processes using:
export LD_PRELOAD=/opt/parastation/lib64/libp4tcp.so
For parallel and serial tasks launched by ParaStation, this environment variable is exported to all processes
by default. Please refer to ps_environment(5).
It's not recommended to insert libp4tcp.so in the global preload configuration file
/etc/ld.so.preload, as this may hang connections to daemon processes started
up before the bypass was configured.
See also p4tcp(8).
5.8. Controlling ParaStation5 communication paths
ParaStation uses different communication paths, see Section 5.1, “ParaStation5 pscom communication
library” for details. In order to restrict the paths to use, a number of environment variables are recognized
by ParaStation.