scheduler - Measure scheduler utilization
Please see following description for synopsis
scheduler(3) Erlang Module Definition scheduler(3)
NAME
scheduler - Measure scheduler utilization
DESCRIPTION
This module contains utility functions for easier measurement and cal-
culation 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. Schedulers that are not online will also be
included. Online schedulers have the lowest 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:uti-
lization(Sample, scheduler:sample_all()).
Note:
Scheduler utilization is measured as an average value over a
time interval, calculated as the difference between two samples.
To get good useful utilization values at least a couple of sec-
onds should have passed between the two samples. For this rea-
son, you should not do
scheduler:utilization(scheduler:sample()). % DO NOT DO THIS!
The above example takes two samples in rapid succession and cal-
culates the scheduler utilization between them. The resulting
values will probably be more misleading than informative.
Instead use scheduler:utilization(Seconds) or let some time pass
between Sample=scheduler:sample() and scheduler:utilization(Sam-
ple).
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.
Ericsson AB runtime_tools 1.17 scheduler(3)