scheduler

Measure scheduler utilization

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).

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.

Functions

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.

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

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()

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