Table of Contents
benchmp, benchmp_getstate, benchmp_interval, start, stop,
get_n, set_n, gettime, settime, get_enough, t_overhead, l_overhead - the
lmbench timing subsystem
#include
typedef u_long iter_t;
typedef
(*bench_f)(iter_t iterations, void* cookie);
typedef (*support_f)(iter_t
iterations, void* cookie);
void benchmp(support_f initialize, bench_f benchmark,
support_f cleanup, int enough, int parallel, int warmup, int repetitions,
void* cookie);
void* benchmp_getstate();
iter_t benchmp_interval(void*
state);
void start(struct timeval *begin);
uint64 stop(struct timeval *begin,
struct timeval *end);
uint64 get_n();
void set_n(uint64 n);
uint64 gettime();
void settime(uint64 u);
uint64 get_enough(uint64 enough);
uint64 t_overhead();
double l_overhead();
The single most important element of a good
benchmarking system is the quality and reliability of its measurement system.
lmbench’s timing subsystem manages the experimental timing process to
produce accurate results in the least possible time. lmbench includes
methods for measuring and eliminating several factors that influence
the accuracy of timing measurements, such as the resolution of the system
clock.
lmbench gets accurate results by considering clock resolution,
auto-sizing the duration of each benchmark, and conducting multiple experiments.
- void benchmp(initialize, benchmark, cleanup, enough, parallel, warmup,
repetitions, cookie)
- measures the performance of benchmark repeatedly
and reports the median result. benchmp creates parallel sub-processes which
run benchmark in parallel. This allows lmbench to measure the system’s ability
to scale as the number of client processes increases. Each sub-process executes
initialize before starting the benchmarking cycle. It will call benchmark
several times in order to collect repetitions results. After all the benchmark
results have been collected, cleanup is called to cleanup any resources
which may have been allocated by initialize or benchmark . cookie is
a void pointer to a hunk of memory that can be used to store any parameters
or state that is needed by the benchmark.
- void benchmp_getstate()
- returns
a void pointer to the lmbench-internal state used during benchmarking.
The state is not to be used or accessed directly by clients, but rather
would be passed into benchmp_interval.
- iter_t benchmp_interval(void* state)
- returns the number of times the benchmark should execute its benchmark
loop during this timing interval. This is used only for weird benchmarks
which cannot implement the benchmark body in a function which can return,
such as the page fault handler. Please see lat_sig.c for sample usage.
- void start(struct timeval *begin)
- starts a timing interval. If begin is
non-null, save the start time in begin .
- uint64 stop(struct timeval *begin,
struct timeval *end)
- stops a timing interval, returning the number of elapsed
micro-seconds.
- uint64 get_n()
- returns the number of times loop_body was
executed during the timing interval.
- void set_n(uint64 n)
- sets the number
of times loop_body was executed during the timing interval.
- uint64 gettime()
- returns the number of micro-seconds in the timing interval.
- void settime(uint64
u)
- sets the number of micro-seconds in the timing interval.
- uint64 get_enough(uint64
enough)
- return the time in micro-seconds needed to accurately measure a
timing interval.
- uint64 t_overhead()
- return the time in micro-seconds needed
to measure time.
- double l_overhead()
- return the time in micro-seconds needed
to do a simple loop.
There are three environment variables that
can be used to modify the lmbench timing subsystem: ENOUGH, TIMING_O,
and LOOP_O. The environment variables can be used to directly set the results
of get_enough , t_overhead , and l_overhead . When running a large number
of benchmarks, or repeating the same benchmark many times, this can save
time by eliminating the necessity of recalculating these values for each
run.
Development of lmbench is continuing.
lmbench(8)
,
lmbench(3)
, reporting(3)
, results(3)
.
Carl Staelin and Larry McVoy
Comments, suggestions, and bug reports are always welcome.
Table of Contents