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+<?xml version="1.0" encoding="utf-8" ?>
+<!DOCTYPE erlref SYSTEM "erlref.dtd">
+
+<erlref>
+ <header>
+ <copyright>
+ <year>2018</year>
+ <holder>Ericsson AB. All Rights Reserved.</holder>
+ </copyright>
+ <legalnotice>
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+
+ </legalnotice>
+
+ <title></title>
+ <prepared></prepared>
+ <responsible></responsible>
+ <docno>1</docno>
+ <approved></approved>
+ <checked></checked>
+ <date></date>
+ <rev></rev>
+ <file>scheduler.xml</file>
+ </header>
+ <module>scheduler</module>
+ <modulesummary>Measure scheduler utilization</modulesummary>
+ <description>
+ <p>This module contains utility functions for easier measurement and
+ calculation of scheduler utilization, otherwise obtained from calling the
+ more primitive <seealso marker="erts:erlang#statistics_scheduler_wall_time">
+ <c>statistics(scheduler_wall_time)</c></seealso>.</p>
+ <p>The simplest usage is to call <seealso marker="#utilization-1">
+ <c>scheduler:utilization(Seconds)</c></seealso>.</p>
+ </description>
+
+ <datatypes>
+ <datatype>
+ <name name="sched_sample"/>
+ </datatype>
+ <datatype>
+ <name name="sched_type"/>
+ </datatype>
+ <datatype>
+ <name name="sched_id"/>
+ </datatype>
+ <datatype>
+ <name name="sched_util_result"/>
+ <desc>
+ <p>A list of tuples containing results for individual schedulers
+ as well as aggregated averages. <c>Util</c> is the scheduler utilization
+ as a floating point value between 0.0 and 1.0. <c>Percent</c> is the
+ same utilization as a more human readable string expressed in percent.</p>
+ <taglist>
+ <tag><c>{normal, SchedulerId, Util, Percent}</c></tag>
+ <item>Scheduler utilization of a normal scheduler with number
+ <c>SchedulerId</c>.</item>
+ <tag><c>{cpu, SchedulerId, Util, Percent}</c></tag>
+ <item>Scheduler utilization of a dirty-cpu scheduler with number
+ <c>SchedulerId</c>.</item>
+ <tag><c>{io, SchedulerId, Util, Percent}</c></tag>
+ <item>Scheduler utilization of a dirty-io scheduler with number
+ <c>SchedulerId</c>. This tuple will only exist if both samples were
+ taken with <seealso marker="#sample_all-0"><c>sample_all/0</c></seealso>.</item>
+ <tag><c>{total, Util, Percent}</c></tag>
+ <item>Total utilization of all normal and dirty-cpu schedulers.</item>
+ <tag><c>{weighted, Util, Percent}</c></tag>
+ <item>Total utilization of all normal and dirty-cpu schedulers,
+ weighted against maximum amount of available CPU time.</item>
+ </taglist>
+ </desc>
+ </datatype>
+ </datatypes>
+
+ <funcs>
+
+ <func>
+ <name name="sample" arity="0"/>
+ <fsummary>Get scheduler utilization sample.</fsummary>
+ <desc>
+ <p>Return a scheduler utilization sample for normal and dirty-cpu
+ schedulers.</p>
+ </desc>
+ </func>
+
+ <func>
+ <name name="sample_all" arity="0"/>
+ <fsummary>Get scheduler utilization sample.</fsummary>
+ <desc>
+ <p>Return a scheduler utilization sample for all schedulers,
+ including dirty-io schedulers.</p>
+ </desc>
+ </func>
+
+ <func>
+ <name name="utilization" arity="1" clause_i="1"/>
+ <fsummary>Measure scheduler utilizations during a period of time.</fsummary>
+ <desc>
+ <p>Measure utilization for normal and dirty-cpu schedulers during
+ <c><anno>Seconds</anno></c> seconds, and then return the result.</p>
+ </desc>
+ </func>
+
+ <func>
+ <name name="utilization" arity="1" clause_i="2"/>
+ <fsummary>Measure scheduler utilizations since sample.</fsummary>
+ <desc>
+ <p>Calculate scheduler utilizations for the time interval from when
+ <c><anno>Sample</anno></c> was taken and "now". The same as calling
+ <c>scheduler:utilization(Sample, scheduler:sample_all())</c>.</p>
+ </desc>
+ </func>
+
+ <func>
+ <name name="utilization" arity="2"/>
+ <fsummary>Measure scheduler utilizations between two samples.</fsummary>
+ <desc>
+ <p>Calculates scheduler utilizations for the time interval between
+ the two samples obtained from calling
+ <seealso marker="#sample-0"><c>sample/0</c></seealso> or
+ <seealso marker="#sample_all-0"><c>sample_all/0</c></seealso>.</p>
+ </desc>
+ </func>
+
+ </funcs>
+ </erlref>