Provided by: lmbench-doc_3.0-a9-1_all
bw_tcp - time data movement through TCP/IP sockets
bw_tcp [ -m <message size> ] [ -M <total bytes> ] [ -P <parallelism> ]
[ -W <warmups> ] [ -N <repetitions> ] server
bw_tcp -S <server>
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
different amount of data. Specifications may end with ``k'' or ``m''
to mean kilobytes (* 1024) or megabytes (* 1024 * 1024).
Output format is Socket bandwidth using localhost: 2.32 MB/sec
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
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).
Funding for the development of this tool was provided by Sun
Microsystems Computer Corporation and Silicon Graphics, Inc.
Carl Staelin and Larry McVoy
Comments, suggestions, and bug reports are always welcome.
(c)1994 Larry McVoy $Date$ BW_TCP(8)