LMBENCH(8)

NAME
lmbench - system benchmarks

DESCRIPTION
lmbench is a series of micro benchmarks intended to measure basic operating system and hardware system metrics. The benchmarks fall into three general classes: bandwidth, latency, and ``other''.

BANDWIDTH MEASUREMENTS
Data movement is fundemental to the performance on most computer systems. The bandwidth measurements are intended to show how the system can move data. The results of the bandwidth metrics can be compared but care must be taken to understand what it is that is being compared. The bandwidth benchmarks can be reduced to two main components: operating system overhead and memory speeds. The bandwidth benchmarks report their results as megabytes moved per second but please note that the data moved is not necessarily the same as the memory bandwidth used to move the data. Consult the individual man pages for more information.

Each of the bandwidth benchmarks is listed below with a brief overview of the intent of the benchmark.

bw_file_rd
    reading and summing of a file via the read(2) interface.

bw_mem
    memory bandwidth (read, write, copy).

bw_mmap_rd
    reading and summing of a file via the memory mapping mmap(2) interface.

bw_pipe
    copying data via a pipe.

bw_unix
    copying data via a Unix socket.

bw_tcp
    reading of data via a TCP/IP socket.

LATENCY MEASUREMENTS
Control messages are also fundemental to the performance on most computer systems. The latency measurements are intended to show how fast a system can be told to do some operation. The results of the latency metrics can be compared to each other for the most part. In particular, the pipe, rpc, tcp, and udp transactions are all identical benchmarks carried out over different system abstractions.

Latency numbers here should mostly be in microseconds per operation.

lat_connect
    the time it takes to establish a TCP/IP connection.

lat_connect_unix
    the time it takes to establish a Unix connection.

lat_ctx
    context switching; the number and size of processes is varied.

lat_fs
    creating and deleting small files.

lat_pagefault
    the time it takes to fault in a page from a file.

lat_mem_rd
    memory read latency (accurate to the ~2-5 nanosecond range, reported in nanoseconds).

lat_mmap
    time to set up a memory mapping.

lat_pipe
    ``hot potato'' transaction through a Unix pipe.

lat_proc
    process creation times (various sorts).

lat_rpc
    ``hot potato'' transaction through Sun RPC over UDP or TCP.

lat_syscall
    non trivial entry into the system.

lat_tcp
    ``hot potato'' transaction through TCP.

lat_udp
    ``hot potato'' transaction through UDP.

OTHER MEASUREMENTS

mhz processor cycle time.

disk
    seek latencies and zone bandwidths.

clock
    timing subsystem parameters.

enough
    timing interval duration required for accurate timing results.

timing_o
    overhead incurred by gettimeofday() to measure timing intervals.

loop_o
    for() loop overhead.

ACKNOWLEDGEMENT
Funding for the development of these tools was provided by Sun Microsystems Computer Corporation.

COPYING
The benchmarking code is distributed under the GPL with additional restrictions, see the COPYING file.

SEE ALSO
lmbench(3), timing(3), results(3), reporting(3), bargraph(1), graph(1), pgraph(1), disk(8), clock(8), enough(8), timing_o(8), loop_o(8), bw_file_rd(8), bw_mem(8), bw_mmap_rd(8), bw_pipe(8), bw_unix(8), lat_connect(8), lat_ctx(8), lat_fcntl(8), lat_fifo(8), lat_fs(8), lat_http(8), lat_mem_rd(8), lat_mmap(8), lat_pagefault(8), lat_pipe(8), lat_proc(8), lat_rpc(8), lat_select(8), lat_syscall(8), lat_tcp(8), lat_udp(8), lat_unix(8), lat_unix_connect(8).