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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).