NAME

bw_pipe - time data movement through pipes

SYNOPSIS

bw_pipe [ -m <message size> ] [ -M <total bytes> ] [ -P <parallelism> ] [ -W <warmups> ] [ -N <repetitions> ]

DESCRIPTION

bw_pipe creates a Unix pipe between two processes and moves total bytes through the pipe in message size chunks (note that pipes are typically sized smaller than that). The default total bytes is 10MB and the default message size is 64KB.

OUTPUT

Output format is "Pipe bandwidth: %0.2f MB/sec\n", megabytes_per_second, i.e.,

Pipe bandwidth: 4.87 MB/sec

MEMORY UTILIZATION

This benchmark can move up to six times the requested memory per process. There are two processes, the sender and the receiver. Most Unix systems implement the read/write system calls as a bcopy from/to kernel space to/from user space. Bcopy will use 2-3 times as much memory bandwidth: there is one read from the source and a write to the destionation. The write usually results in a cache line read and then a write back of the cache line at some later point. Memory utilization might be reduced by 1/3 if the processor architecture implemented "load cache line" and "store cache line" instructions (as well as getcachelinesize).

ACKNOWLEDGEMENT

Funding for the development of this tool was provided by Sun Microsystems Computer Corporation.

AUTHOR

Carl Staelin and Larry McVoy

Comments, suggestions, and bug reports are always welcome.