is a client/server program that moves data over a TCP/IP socket. Nothing is
done with the data on either side;
of data is moved in
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.
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.