1scheduler(3)               Erlang Module Definition               scheduler(3)
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NAME

6       scheduler - Measure scheduler utilization
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DESCRIPTION

9       This  module contains utility functions for easier measurement and cal‐
10       culation of scheduler utilization, otherwise obtained from calling  the
11       more primitive statistics(scheduler_wall_time).
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13       The simplest usage is to call scheduler:utilization(Seconds).
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DATA TYPES

16       sched_sample()
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18       sched_type() = normal | cpu | io
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20       sched_id() = integer()
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22       sched_util_result() =
23           [{sched_type(), sched_id(), float(), string()} |
24            {total, float(), string()} |
25            {weighted, float(), string()}]
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27              A list of tuples containing results for individual schedulers as
28              well as aggregated averages. Util is the  scheduler  utilization
29              as  a  floating  point value between 0.0 and 1.0. Percent is the
30              same utilization as a more human readable  string  expressed  in
31              percent.
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33                {normal, SchedulerId, Util, Percent}:
34                  Scheduler  utilization  of  a  normal  scheduler with number
35                  SchedulerId. Schedulers that are not online will also be in‐
36                  cluded. Online schedulers have the lowest SchedulerId.
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38                {cpu, SchedulerId, Util, Percent}:
39                  Scheduler  utilization  of a dirty-cpu scheduler with number
40                  SchedulerId.
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42                {io, SchedulerId, Util, Percent}:
43                  Scheduler utilization of a dirty-io  scheduler  with  number
44                  SchedulerId. This tuple will only exist if both samples were
45                  taken with sample_all/0.
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47                {total, Util, Percent}:
48                  Total utilization of all normal and dirty-cpu schedulers.
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50                {weighted, Util, Percent}:
51                  Total utilization of all normal  and  dirty-cpu  schedulers,
52                  weighted against maximum amount of available CPU time.
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EXPORTS

55       sample() -> sched_sample()
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57              Return  a  scheduler utilization sample for normal and dirty-cpu
58              schedulers.
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60       sample_all() -> sched_sample()
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62              Return a scheduler utilization sample for  all  schedulers,  in‐
63              cluding dirty-io schedulers.
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65       utilization(Seconds) -> sched_util_result()
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67              Types:
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69                 Seconds = integer() >= 1
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71              Measure  utilization  for normal and dirty-cpu schedulers during
72              Seconds seconds, and then return the result.
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74       utilization(Sample) -> sched_util_result()
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76              Types:
77
78                 Sample = sched_sample()
79
80              Calculate scheduler utilizations for the time interval from when
81              Sample  was  taken and "now". The same as calling scheduler:uti‐
82              lization(Sample, scheduler:sample_all()).
83
84          Note:
85              Scheduler utilization is measured as an  average  value  over  a
86              time interval, calculated as the difference between two samples.
87              To get good useful utilization values at least a couple of  sec‐
88              onds  should  have passed between the two samples. For this rea‐
89              son, you should not do
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91              scheduler:utilization(scheduler:sample()). % DO NOT DO THIS!
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93
94              The above example takes two samples in rapid succession and cal‐
95              culates  the  scheduler  utilization between them. The resulting
96              values will probably be more misleading than informative.
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98              Instead use scheduler:utilization(Seconds) or let some time pass
99              between Sample=scheduler:sample() and scheduler:utilization(Sam‐
100              ple).
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102
103       utilization(Sample1, Sample2) -> sched_util_result()
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105              Types:
106
107                 Sample1 = Sample2 = sched_sample()
108
109              Calculates scheduler utilizations for the time interval  between
110              the two samples obtained from calling sample/0 or sample_all/0.
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114Ericsson AB                   runtime_tools 1.17                  scheduler(3)