Provided by: lmbench-doc_3.0-a9-1.1_all 
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''.
Most of the lmbench benchmarks use a standard timing harness described in timing(3) and
have a few standard options: parallelism, warmup, and repetitions. Parallelism specifies
the number of benchmark processes to run in parallel. This is primarily useful when
measuring the performance of SMP or distributed computers and can be used to evaluate the
system's performance scalability. Warmup is the number of minimum number of microseconds
the benchmark should execute the benchmarked capability before it begins measuring
performance. Again this is primarily useful for SMP or distributed systems and it is
intended to give the process scheduler time to "settle" and migrate processes to other
processors. By measuring performance over various warmup periods, users may evaulate the
scheduler's responsiveness. Repetitions is the number of measurements that the benchmark
should take. This allows lmbench to provide greater or lesser statistical strength to the
results it reports. The default number of repetitions is 11.
BANDWIDTH MEASUREMENTS
Data movement is fundamental 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_cp memory copy.
bw_mem_rd memory reading and summing.
bw_mem_wr memory writing.
bw_mmap_rd reading and summing of a file via the memory mapping mmap(2) interface.
bw_pipe reading of data via a pipe.
bw_tcp reading of data via a TCP/IP socket.
bw_unix reading data from a UNIX socket.
LATENCY MEASUREMENTS
Control messages are also fundamental 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_ctx context switching; the number and size of processes is varied.
lat_fcntl fcntl file locking.
lat_fifo ``hot potato'' transaction through a UNIX FIFO.
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_ops basic processor operations, such as integer XOR, ADD, SUB, MUL, DIV, and
MOD, and float ADD, MUL, DIV, and double ADD, MUL, DIV.
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_select select latency
lat_sig signal installation and catch latencies. Also protection fault signal
latency.
lat_syscall non trivial entry into the system.
lat_tcp ``hot potato'' transaction through TCP.
lat_udp ``hot potato'' transaction through UDP.
lat_unix ``hot potato'' transaction through UNIX sockets.
lat_unix_connect
the time it takes to establish a UNIX socket connection.
OTHER MEASUREMENTS
mhz processor cycle time
tlb TLB size and TLB miss latency
line cache line size (in bytes)
cache cache statistics, such as line size, cache sizes, memory parallelism.
stream John McCalpin's stream benchmark
par_mem memory subsystem parallelism. How many requests can the memory subsystem
service in parallel, which may depend on the location of the data in the
memory hierarchy.
par_ops basic processor operation parallelism.
SEE ALSO
bargraph(1), graph(1), lmbench(3), results(3), timing(3), bw_file_rd(8), bw_mem_cp(8),
bw_mem_wr(8), bw_mmap_rd(8), bw_pipe(8), bw_tcp(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_ops(8), lat_pagefault(8), lat_pipe(8), lat_proc(8), lat_rpc(8), lat_select(8),
lat_sig(8), lat_syscall(8), lat_tcp(8), lat_udp(8), lmdd(8), par_ops(8), par_mem(8),
mhz(8), tlb(8), line(8), cache(8), stream(8)
ACKNOWLEDGEMENT
Funding for the development of these tools was provided by Sun Microsystems Computer
Corporation.
A large number of people have contributed to the testing and development of lmbench.
COPYING
The benchmarking code is distributed under the GPL with additional restrictions, see the
COPYING file.
AUTHOR
Carl Staelin and Larry McVoy
Comments, suggestions, and bug reports are always welcome.
(c)1994-2000 Larry McVoy and Carl Staelin $Date$ LMBENCH(8)