scheduler(3)

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.