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BW_TCP(1)			    LMBENCH			     BW_TCP(1)

NAME
       bw_tcp -	time data movement through TCP/IP sockets

SYNOPSIS
       bw_tcp  [ -m _message size_ ] [ -M _total bytes_	] [ -P _parallelism_ ]
       [ -W _warmups_ ]	[ -N _repetitions_ ] server
       bw_tcp -s
       bw_tcp -S _server_

DESCRIPTION
       bw_tcp is a client/server program that moves data over a	TCP/IP socket.
       Nothing	is  done  with the data	on either side;	total bytes of data is
       moved in	message	size chunks.

       bw_tcp has three	forms of usage:	as a server (-s), as a client  (bw_tcp
       localhost), and as a shutdown (bw_tcp -S	localhost).

       The default amount of data is 10MB.  The	client form may	specify	a dif-
       ferent amount of	data.  Specifications may end with ``k'' or  ``m''  to
       mean kilobytes (* 1024) or megabytes (* 1024 * 1024).

OUTPUT
       Output format is	Socket bandwidth using localhost: 2.32 MB/sec

MEMORY UTILIZATION
       This  benchmark	can  move  up  to  six	times the requested memory per
       process when run	through	the loopback device.  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  usu-
       ally  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  Microsys-
       tems Computer Corporation and Silicon Graphics, Inc.

SEE ALSO
       lmbench(8).

AUTHOR
       Carl Staelin and	Larry McVoy

       Comments, suggestions, and bug reports are always welcome.

(c)1994	Larry McVoy		    $Date$			     BW_TCP(1)

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

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