[Beowulf] MPICH ch_p4 compile vs runtime options - bufsize, pkt_size, socksize

[Bill Wichser]

Can anyone explain to me what the various options for MPICH compilation 
versus what the runtime options would provide?

For example, when compiling MPICH-1.2.6 I have the options:

-socksize=BYTES
which state "changes the size of the socket buffers used."

-pkt_size=LENGTH
allows you to choose the message length at which the ADI switches from 
its short to long message format.


And for runtime I have:
a.out -p4sctrl bufsize=KBYTES
which controls the soket buffer size

The environment variables:
P4_SOCKBUFSIZE - defines the socket buffer size in bytes

Now in all cases I will also assume that the system-wide TCP settings 
have also been increased (net.core.[rw]mem_max, net.ipv4.tcp_[ rw]mem) 
in order to support sizes allowed in the above.

Except for optimizing -pkt_size I am under the belief that all the 
others are effectively one and the same.

Thanks,
Bill