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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
       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.

VARIABLES
       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.

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)