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lmbench timing(3) LMBENCH lmbench timing(3) NAME benchmp, benchmp_getstate, benchmp_interval, start, stop, get_n, set_n, gettime, settime, get_enough, t_overhead, l_overhead - the lmbench timing subsystem SYNOPSIS #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(); DESCRIPTION The single most important element of a good benchmarking system is the quality and reliability of its measurement system. lmbench's timing sub- system 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 measure- ments, 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, rep- etitions, cookie) measures the performance of benchmark repeatedly and reports the me- dian 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 cy- cle. It will call benchmark several times in order to collect repe- titions results. After all the benchmark results have been col- lected, 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 bench- mark 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-sec- onds. 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 tim- ing 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. VARIABLES There are three environment variables that can be used to modify the lm- bench timing subsystem: ENOUGH, TIMING_O, and LOOP_O. The environment variables can be used to directly set the results of get_enough , t_over- head , and l_overhead . When running a large number of benchmarks, or re- peating the same benchmark many times, this can save time by eliminating the necessity of recalculating these values for each run. FUTURES Development of lmbench is continuing. SEE ALSO lmbench(8), lmbench(3), reporting(3), results(3). AUTHOR Carl Staelin and Larry McVoy Comments, suggestions, and bug reports are always welcome. (c)1998 Larry McVoy $Date:$ lmbench timing(3)
NAME | SYNOPSIS | DESCRIPTION | VARIABLES | FUTURES | SEE ALSO | AUTHOR
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