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)