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BW_PIPE(8)			    LMBENCH			    BW_PIPE(8)

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  de-
       fault message size is 64KB.

OUTPUT
       Output  format  is "Pipe	bandwidth: %0.2f MB/sec\n", megabytes_per_sec-
       ond, 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 mem-
       ory 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 getcacheli-
       nesize).

ACKNOWLEDGEMENT
       Funding	for the	development of this tool was provided by Sun Microsys-
       tems Computer Corporation.

SEE ALSO
       lmbench(8).

AUTHOR
       Carl Staelin and	Larry McVoy

       Comments, suggestions, and bug reports are always welcome.

(c)1994	Larry McVoy		    $Date$			    BW_PIPE(8)

NAME | SYNOPSIS | DESCRIPTION | OUTPUT | MEMORY UTILIZATION | ACKNOWLEDGEMENT | SEE ALSO | AUTHOR

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