NAME

       scheduler - Measure scheduler utilization

DESCRIPTION

       This module contains utility functions for easier measurement and calculation of scheduler
       utilization,    otherwise     obtained     from     calling     the     more     primitive
       statistics(scheduler_wall_time).

       The simplest usage is to call scheduler:utilization(Seconds).

DATA TYPES

       sched_sample()

       sched_type() = normal | cpu | io

       sched_id() = integer()

       sched_util_result() =
           [{sched_type(), sched_id(), float(), string()} |
            {total, float(), string()} |
            {weighted, float(), string()}]

              A list of tuples containing results for individual schedulers as well as aggregated
              averages. Util is the scheduler utilization as a floating point value  between  0.0
              and  1.0. Percent is the same utilization as a more human readable string expressed
              in percent.

                {normal, SchedulerId, Util, Percent}:
                  Scheduler utilization of a normal scheduler with number SchedulerId.

                {cpu, SchedulerId, Util, Percent}:
                  Scheduler utilization of a dirty-cpu scheduler with number SchedulerId.

                {io, SchedulerId, Util, Percent}:
                  Scheduler utilization of a dirty-io scheduler  with  number  SchedulerId.  This
                  tuple will only exist if both samples were taken with sample_all/0.

                {total, Util, Percent}:
                  Total utilization of all normal and dirty-cpu schedulers.

                {weighted, Util, Percent}:
                  Total  utilization  of  all  normal  and dirty-cpu schedulers, weighted against
                  maximum amount of available CPU time.

EXPORTS

       sample() -> sched_sample()

              Return a scheduler utilization sample for normal and dirty-cpu schedulers.

       sample_all() -> sched_sample()

              Return a scheduler  utilization  sample  for  all  schedulers,  including  dirty-io
              schedulers.

       utilization(Seconds) -> sched_util_result()

              Types:

                 Seconds = integer() >= 1

              Measure utilization for normal and dirty-cpu schedulers during Seconds seconds, and
              then return the result.

       utilization(Sample) -> sched_util_result()

              Types:

                 Sample = sched_sample()

              Calculate scheduler utilizations for the time interval from when Sample  was  taken
              and     "now".     The     same     as     calling    scheduler:utilization(Sample,
              scheduler:sample_all()).

       utilization(Sample1, Sample2) -> sched_util_result()

              Types:

                 Sample1 = Sample2 = sched_sample()

              Calculates scheduler utilizations for the time interval  between  the  two  samples
              obtained from calling sample/0 or sample_all/0.