Provided by: erlang-manpages_22.2.7+dfsg-1_all bug

NAME

       msacc - Convenience functions for microstate accounting

DESCRIPTION

       This  module  implements  some  convenience  functions for analyzing microstate accounting
       data. For details about how to use the basic api and what the different  states  represent
       see  erlang:statistics(microstate_accounting).

       Basic Scenario

       1> msacc:start(1000).
       ok
       2> msacc:print().
       Average thread real-time    : 1000513 us
       Accumulated system run-time :    2213 us
       Average scheduler run-time  :    1076 us

               Thread      aux check_io emulator       gc    other     port    sleep

       Stats per thread:
            async( 0)    0.00%    0.00%    0.00%    0.00%    0.00%    0.00%  100.00%
            async( 1)    0.00%    0.00%    0.00%    0.00%    0.00%    0.00%  100.00%
              aux( 1)    0.00%    0.00%    0.00%    0.00%    0.00%    0.00%   99.99%
        scheduler( 1)    0.00%    0.03%    0.13%    0.00%    0.01%    0.00%   99.82%
        scheduler( 2)    0.00%    0.00%    0.00%    0.00%    0.03%    0.00%   99.97%

       Stats per type:
                async    0.00%    0.00%    0.00%    0.00%    0.00%    0.00%  100.00%
                  aux    0.00%    0.00%    0.00%    0.00%    0.00%    0.00%   99.99%
            scheduler    0.00%    0.02%    0.06%    0.00%    0.02%    0.00%   99.89%
       ok

       This  first  command  enables  microstate  accounting  for 1000 milliseconds. See start/0,
       stop/0, reset/0 and start/1 for more details. The second  command  prints  the  statistics
       gathered during that time. First three general statistics are printed.

         Average real-time:
           The  average  time  spent  collecting data in the threads. This should be close to the
           time which data was collected.

         System run-time:
           The total run-time of all threads in the system. This is what  you  get  if  you  call
           msacc:stats(total_runtime,Stats).

         Average scheduler run-time:
           The  average  run-time  for  the  schedulers.  This  is the average amount of time the
           schedulers did not sleep.

       Then one column per state is printed with a the percentage of time this  thread  spent  in
       the  state out of it's own real-time. After the thread specific time, the accumulated time
       for each type of thread is printed in a similar format.

       Since we have the average real-time and the percentage spent in each state we  can  easily
       calculate the time spent in each state by multiplying Average thread real-time with Thread
       state %, i.e. to get the time Scheduler 1 spent in the emulator state we  do  1000513us  *
       0.13% = 1300us.

DATA TYPES

       msacc_data() = [msacc_data_thread()]

       msacc_data_thread() =
           #{'$type' := msacc_data,
             type := msacc_type(),
             id := msacc_id(),
             counters := msacc_data_counters()}

       msacc_data_counters() = #{msacc_state() => integer() >= 0}

              A  map  containing  the  different  microstate  accounting states and the number of
              microseconds spent in it.

       msacc_stats() = [msacc_stats_thread()]

       msacc_stats_thread() =
           #{'$type' := msacc_stats,
             type := msacc_type(),
             id := msacc_id(),
             system := float(),
             counters := msacc_stats_counters()}

              A map containing information about a specific thread. The percentages  in  the  map
              can  be  either  run-time  or  real-time  depending  on  if runtime or realtime was
              requested from stats/2. system is the percentage of  total  system  time  for  this
              specific thread.

       msacc_stats_counters() =
           #{msacc_state() => #{thread := float(), system := float()}}

              A  map containing the different microstate accounting states. Each value in the map
              contains another map with the percentage of time that this thread has spent in  the
              specific  state.  Both the percentage of system time and the time for that specific
              thread is part of the map.

       msacc_type() =
           aux | async | dirty_cpu_scheduler | dirty_io_scheduler |
           poll | scheduler

       msacc_id() = integer() >= 0

       msacc_state() =
           alloc | aux | bif | busy_wait | check_io | emulator | ets |
           gc | gc_fullsweep | nif | other | port | send | sleep | timers

              The    different    states     that     a     thread     can     be     in.     See
              erlang:statistics(microstate_accounting) for details.

       msacc_print_options() = #{system => boolean()}

              The different options that can be given to print/2.

EXPORTS

       available() -> boolean()

              This function checks whether microstate accounting is available or not.

       start() -> boolean()

              Start microstate accounting. Returns whether it was previously enabled or disabled.

       start(Time) -> true

              Types:

                 Time = timeout()

              Resets   all   counters  and  then  starts  microstate  accounting  for  the  given
              milliseconds.

       stop() -> boolean()

              Stop microstate accounting. Returns whether is was previously enabled or disabled.

       reset() -> boolean()

              Reset microstate accounting counters. Returns whether is was enabled or disabled.

       print() -> ok

              Prints   the   current   microstate   accounting   to   standard   out.   Same   as
              msacc:print(msacc:stats(),#{}).

       print(DataOrStats) -> ok

              Types:

                 DataOrStats = msacc_data() | msacc_stats()

              Print    the    given   microstate   statistics   values   to   stdout.   Same   as
              msacc:print(DataOrStats,#{}).

       print(DataOrStats, Options) -> ok

              Types:

                 DataOrStats = msacc_data() | msacc_stats()
                 Options = msacc_print_options()

              Print the given microstate statistics values to standard out. With many states this
              can  be quite verbose. See the top of this reference manual for a brief description
              of what the fields mean.

              It is possible to print more specific types of statistics by first manipulating the
              DataOrStats using stats/2. For instance if you want to print the percentage of run-
              time for each thread you can do:

              msacc:print(msacc:stats(runtime,msacc:stats())).

              If you want to only print run-time per thread type you can do:

              msacc:print(msacc:stats(type,msacc:stats(runtime,msacc:stats()))).

              Options

                system:
                  Print percentage of time spent in each state out of  system  time  as  well  as
                  thread time. Default: false.

       print(FileOrDevice, DataOrStats, Options) -> ok

              Types:

                 FileOrDevice = file:filename() | io:device()
                 DataOrStats = msacc_data() | msacc_stats()
                 Options = msacc_print_options()

              Print the given microstate statistics values to the given file or device. The other
              arguments behave the same way as for print/2.

       stats() -> msacc_data()

              Returns a runtime system independent version  of  the  microstate  statistics  data
              presented  by  erlang:statistics(microstate_accounting).  All  counters  have  been
              normalized to be in microsecond resolution.

       stats(Analysis, Stats) -> integer() >= 0

              Types:

                 Analysis = system_realtime | system_runtime
                 Stats = msacc_data()

              Returns the system time for the given microstate statistics values. System time  is
              the accumulated time of all threads.

                realtime:
                  Returns all time recorded for all threads.

                runtime:
                  Returns  all  time spent doing work for all threads, i.e. all time not spent in
                  the sleep state.

       stats(Analysis, Stats) -> msacc_stats()

              Types:

                 Analysis = realtime | runtime
                 Stats = msacc_data()

              Returns fractions of real-time or run-time spent in the various  threads  from  the
              given microstate statistics values.

       stats(Analysis, StatsOrData) -> msacc_data() | msacc_stats()

              Types:

                 Analysis = type
                 StatsOrData = msacc_data() | msacc_stats()

              Returns  a list of microstate statistics values where the values for all threads of
              the same type has been merged.

       to_file(Filename) -> ok | {error, file:posix()}

              Types:

                 Filename = file:name_all()

              Dumps the current microstate statistics counters to a file that can be parsed  with
              file:consult/1.

       from_file(Filename) -> msacc_data()

              Types:

                 Filename = file:name_all()

              Read a file dump produced by  to_file(Filename).