.TH scheduler 3erl "runtime_tools 1.15.1" "Ericsson AB" "Erlang Module Definition"
.SH NAME
scheduler \- Measure scheduler utilization
.SH DESCRIPTION
.LP
This module contains utility functions for easier measurement and calculation of scheduler utilization, otherwise obtained from calling the more primitive \fIstatistics(scheduler_wall_time)\fR\&\&.
.LP
The simplest usage is to call \fIscheduler:utilization(Seconds)\fR\&\&.
.SH DATA TYPES
.nf

\fBsched_sample()\fR\&
.br
.fi
.nf

\fBsched_type()\fR\& = normal | cpu | io
.br
.fi
.nf

\fBsched_id()\fR\& = integer()
.br
.fi
.nf

\fBsched_util_result()\fR\& = 
.br
    [{sched_type(), sched_id(), float(), string()} |
.br
     {total, float(), string()} |
.br
     {weighted, float(), string()}]
.br
.fi
.RS
.LP
A list of tuples containing results for individual schedulers as well as aggregated averages\&. \fIUtil\fR\& is the scheduler utilization as a floating point value between 0\&.0 and 1\&.0\&. \fIPercent\fR\& is the same utilization as a more human readable string expressed in percent\&.
.RS 2
.TP 2
.B
\fI{normal, SchedulerId, Util, Percent}\fR\&:
Scheduler utilization of a normal scheduler with number \fISchedulerId\fR\&\&.
.TP 2
.B
\fI{cpu, SchedulerId, Util, Percent}\fR\&:
Scheduler utilization of a dirty-cpu scheduler with number \fISchedulerId\fR\&\&.
.TP 2
.B
\fI{io, SchedulerId, Util, Percent}\fR\&:
Scheduler utilization of a dirty-io scheduler with number \fISchedulerId\fR\&\&. This tuple will only exist if both samples were taken with \fIsample_all/0\fR\&\&.
.TP 2
.B
\fI{total, Util, Percent}\fR\&:
Total utilization of all normal and dirty-cpu schedulers\&.
.TP 2
.B
\fI{weighted, Util, Percent}\fR\&:
Total utilization of all normal and dirty-cpu schedulers, weighted against maximum amount of available CPU time\&.
.RE
.RE

.SH EXPORTS
.LP
.nf

.B
sample() -> sched_sample()
.br
.fi
.br
.RS
.LP
Return a scheduler utilization sample for normal and dirty-cpu schedulers\&.
.RE

.LP
.nf

.B
sample_all() -> sched_sample()
.br
.fi
.br
.RS
.LP
Return a scheduler utilization sample for all schedulers, including dirty-io schedulers\&.
.RE

.LP
.nf

.B
utilization(Seconds) -> sched_util_result()
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Seconds = integer() >= 1
.br
.RE
.RE
.RS
.LP
Measure utilization for normal and dirty-cpu schedulers during \fISeconds\fR\& seconds, and then return the result\&.
.RE

.LP
.nf

.B
utilization(Sample) -> sched_util_result()
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Sample = sched_sample()
.br
.RE
.RE
.RS
.LP
Calculate scheduler utilizations for the time interval from when \fISample\fR\& was taken and "now"\&. The same as calling \fIscheduler:utilization(Sample, scheduler:sample_all())\fR\&\&.
.RE

.LP
.nf

.B
utilization(Sample1, Sample2) -> sched_util_result()
.br
.fi
.br
.RS
.LP
Types:

.RS 3
Sample1 = Sample2 = sched_sample()
.br
.RE
.RE
.RS
.LP
Calculates scheduler utilizations for the time interval between the two samples obtained from calling \fIsample/0\fR\& or \fIsample_all/0\fR\&\&.
.RE