diff options
Diffstat (limited to 'erts/doc/src/erlang.xml')
| -rw-r--r-- | erts/doc/src/erlang.xml | 188 |
1 files changed, 175 insertions, 13 deletions
diff --git a/erts/doc/src/erlang.xml b/erts/doc/src/erlang.xml index d3aad94660..803da382ed 100644 --- a/erts/doc/src/erlang.xml +++ b/erts/doc/src/erlang.xml @@ -131,6 +131,17 @@ </note> </item> + <tag><c>perf_counter</c></tag> + <item><p>Symbolic representation of the performance counter + time unit used by the Erlang runtime system.</p> + + <p>The <c>perf_counter</c> time unit behaves much in the same way + as the <c>native</c> time unit. That is it might differ inbetween + run-time restarts. You get values of this type by calling + <seealso marker="kernel:os#perf_counter/0"><c>os:perf_counter()</c></seealso> + </p> + </item> + </taglist> <p>The <c>time_unit/0</c> type may be extended. Use @@ -5859,6 +5870,146 @@ true</pre> <func> <name name="statistics" arity="1" clause_i="6"/> + <fsummary>Information about microstate accounting.</fsummary> + <desc> + <marker id="statistics_microstate_accounting"></marker> + <p> + Microstate accounting can be used to measure how much time the Erlang + runtime system spends doing various tasks. It is designed to be as + lightweight as possible, but there will be some overhead when this + is enabled. Microstate accounting is meant to be a profiling tool + to help figure out performance bottlenecks. + To <c>start</c>/<c>stop</c>/<c>reset</c> microstate_accounting you use + the system_flag + <seealso marker="#system_flag_microstate_accounting"> + <c>microstate_accounting</c></seealso>. + </p> + <p> + <c>erlang:statistics(microstate_accounting)</c> returns a list of maps + representing some of the OS threads within ERTS. Each map contains + <c>type</c> and <c>id</c> fields that can be used to identify what + thread it is, and also a counters field that contains data about how + much time has been spent in the various states.</p> + <pre> +> <input>erlang:statistics(microstate_accounting).</input> +[#{counters => #{aux => 1899182914, + check_io => 2605863602, + emulator => 45731880463, + gc => 1512206910, + other => 5421338456, + port => 221631, + sleep => 5150294100}, + id => 1, + type => scheduler}|...] + </pre> + <p>The time unit is the same as returned by + <seealso marker="kernel:os#perf_counter/0"> + <c>os:perf_counter/0</c></seealso>. + So to convert it to milliseconds you could do something like this:</p> + <pre> +lists:map( + fun(#{ counters := Cnt } = M) -> + MsCnt = maps:map(fun(_K, PerfCount) -> + erlang:convert_time_unit(PerfCount, perf_counter, 1000) + end, Cnt), + M#{ counters := MsCnt } + end, erlang:statistics(microstate_accounting)). + </pre> + <p> + It is important to note that these values are not guaranteed to be + the exact time spent in each state. This is because of various + optimisation done in order to keep the overhead as small as possible. + </p> + + <p>Currently the following <c><anno>MSAcc_Thread_Type</anno></c> are available:</p> + <taglist> + <tag><c>scheduler</c></tag> + <item>The main execution threads that do most of the work.</item> + <tag><c>async</c></tag><item>Async threads are used by various + linked-in drivers (mainly the file drivers) do offload non-cpu + intensive work.</item> + <tag><c>aux</c></tag><item>Takes care of any work that is not + specifically assigned to a scheduler.</item> + </taglist> + <p>Currently the following <c><anno>MSAcc_Thread_State</anno></c>s are available. + All states are exclusive, meaning that a thread cannot be in two states + at once. So if you add the numbers of all counters in a thread + you will get the total run-time for that thread.</p> + <taglist> + <tag><c>aux</c></tag> + <item>Time spent handling auxiliary jobs.</item> + <tag><c>check_io</c></tag> + <item>Time spent checking for new I/O events.</item> + <tag><c>emulator</c></tag> + <item>Time spent executing erlang processes.</item> + <tag><c>gc</c></tag> + <item>Time spent doing garbage collection. When extra states are + enabled this is the time spent doing non-fullsweep garbage + collections.</item> + <tag><c>other</c></tag> + <item>Time spent doing unaccounted things.</item> + <tag><c>port</c></tag> + <item>Time spent executing ports.</item> + <tag><c>sleep</c></tag> + <item>Time spent sleeping.</item> + </taglist> + <p>It is possible to add more fine grained <c><anno>MSAcc_Thread_State</anno></c>s + through configure. + (e.g. <c>./configure --with-microstate-accounting=extra</c>). + Enabling these states will cause a performance degradation when + microstate accounting is turned off and increase the overhead when + it is turned on.</p> + <taglist> + <tag><c>alloc</c></tag> + <item>Time spent managing memory. Without extra states this time is + spread out over all other states.</item> + <tag><c>bif</c></tag> + <item>Time spent in bifs. Without extra states this time is part of + the <c>emulator</c> state.</item> + <tag><c>busy_wait</c></tag> + <item>Time spent busy waiting. This is also the state where a + scheduler no longer reports that it is active when using + <seealso marker="#statistics_scheduler_wall_time"> + <c>erlang:statistics(scheduler_wall_time)</c></seealso>. + So if you add all other states but this and sleep and then divide that + by all time in the thread you should get something very similar to the + scheduler_wall_time fraction. Without extra states this time is part + of the <c>other</c> state.</item> + <tag><c>ets</c></tag> + <item>Time spent executing ETS bifs. Without extra states this time is + part of the <c>emulator</c> state.</item> + <tag><c>gc_full</c></tag> + <item>Time spent doing fullsweep garbage collection. Without extra + states this time is part of the <c>gc</c> state.</item> + <tag><c>nif</c></tag> + <item>Time spent in nifs. Without extra states this time is part of + the <c>emulator</c> state.</item> + <tag><c>send</c></tag> + <item>Time spent sending messages (processes only). Without extra + states this time is part of the <c>emulator</c> state.</item> + <tag><c>timers</c></tag> + <item>Time spent managing timers. Without extra states this time is + part of the <c>other</c> state.</item> + </taglist> + <p>There is a utility module called + <seealso marker="runtime_tools:msacc"><c>msacc</c></seealso> in + runtime_tools that can be used to more easily analyse these + statistics.</p> + + <p> + Returns <c>undefined</c> if the system flag + <seealso marker="#system_flag_microstate_accounting"> + <c>microstate_accounting</c></seealso> + is turned off. + </p> + <p>The list of thread information is unsorted and may appear in + different order between calls.</p> + <note><p>The threads and states are subject to change without any + prior notice.</p></note> + </desc> + </func> + <func> + <name name="statistics" arity="1" clause_i="7"/> <fsummary>Information about reductions.</fsummary> <desc> <marker id="statistics_reductions"></marker> @@ -5876,7 +6027,7 @@ true</pre> </func> <func> - <name name="statistics" arity="1" clause_i="7"/> + <name name="statistics" arity="1" clause_i="8"/> <fsummary>Information about the run-queues.</fsummary> <desc><marker id="statistics_run_queue"></marker> <p> @@ -5892,7 +6043,7 @@ true</pre> </func> <func> - <name name="statistics" arity="1" clause_i="8"/> + <name name="statistics" arity="1" clause_i="9"/> <fsummary>Information about the run-queue lengths.</fsummary> <desc><marker id="statistics_run_queue_lengths"></marker> <p> @@ -5912,7 +6063,7 @@ true</pre> </func> <func> - <name name="statistics" arity="1" clause_i="9"/> + <name name="statistics" arity="1" clause_i="10"/> <fsummary>Information about runtime.</fsummary> <desc> <p>Returns information about runtime, in milliseconds.</p> @@ -5927,7 +6078,7 @@ true</pre> </func> <func> - <name name="statistics" arity="1" clause_i="10"/> + <name name="statistics" arity="1" clause_i="11"/> <fsummary>Information about each schedulers work time.</fsummary> <desc> <marker id="statistics_scheduler_wall_time"></marker> @@ -5998,7 +6149,7 @@ ok </func> <func> - <name name="statistics" arity="1" clause_i="11"/> + <name name="statistics" arity="1" clause_i="12"/> <fsummary>Information about active processes and ports.</fsummary> <desc><marker id="statistics_total_active_tasks"></marker> <p> @@ -6016,7 +6167,7 @@ ok </func> <func> - <name name="statistics" arity="1" clause_i="12"/> + <name name="statistics" arity="1" clause_i="13"/> <fsummary>Information about the run-queue lengths.</fsummary> <desc><marker id="statistics_total_run_queue_lengths"></marker> <p> @@ -6035,7 +6186,7 @@ ok </func> <func> - <name name="statistics" arity="1" clause_i="13"/> + <name name="statistics" arity="1" clause_i="14"/> <fsummary>Information about wall clock.</fsummary> <desc> <p>Returns information about wall clock. <c>wall_clock</c> can @@ -6269,6 +6420,17 @@ ok <func> <name name="system_flag" arity="2" clause_i="5"/> + <fsummary>Set system flag microstate_accounting</fsummary> + <desc><p><marker id="system_flag_microstate_accounting"></marker> + Turns on/off microstate accounting measurements. By passing reset it is possible to reset + all counters to 0.</p> + <p>For more information see, + <seealso marker="#statistics_microstate_accounting">erlang:statistics(microstate_accounting)</seealso>. + </p> + </desc> + </func> + <func> + <name name="system_flag" arity="2" clause_i="6"/> <fsummary>Sets system flag <c>min_heap_size</c>.</fsummary> <desc> <p>Sets the default minimum heap size for processes. The size @@ -6283,7 +6445,7 @@ ok </func> <func> - <name name="system_flag" arity="2" clause_i="6"/> + <name name="system_flag" arity="2" clause_i="7"/> <fsummary>Sets system flag <c>min_bin_vheap_size</c>.</fsummary> <desc> <p>Sets the default minimum binary virtual heap size for @@ -6300,7 +6462,7 @@ ok </func> <func> - <name name="system_flag" arity="2" clause_i="7"/> + <name name="system_flag" arity="2" clause_i="8"/> <fsummary>Sets system flag <c>multi_scheduling</c>.</fsummary> <desc> <p><marker id="system_flag_multi_scheduling"></marker> @@ -6338,7 +6500,7 @@ ok </func> <func> - <name name="system_flag" arity="2" clause_i="8"/> + <name name="system_flag" arity="2" clause_i="9"/> <fsummary>Sets system flag <c>scheduler_bind_type</c>.</fsummary> <type name="scheduler_bind_type"/> <desc> @@ -6456,7 +6618,7 @@ ok </func> <func> - <name name="system_flag" arity="2" clause_i="9"/> + <name name="system_flag" arity="2" clause_i="10"/> <fsummary>Sets system flag <c>scheduler_wall_time</c>.</fsummary> <desc><p><marker id="system_flag_scheduler_wall_time"></marker> Turns on or off scheduler wall time measurements.</p> @@ -6466,7 +6628,7 @@ ok </func> <func> - <name name="system_flag" arity="2" clause_i="10"/> + <name name="system_flag" arity="2" clause_i="11"/> <fsummary>Sets system flag <c>schedulers_online</c>.</fsummary> <desc> <p><marker id="system_flag_schedulers_online"></marker> @@ -6491,7 +6653,7 @@ ok </func> <func> - <name name="system_flag" arity="2" clause_i="11"/> + <name name="system_flag" arity="2" clause_i="12"/> <fsummary>Sets system flag <c>trace_control_word</c>.</fsummary> <desc> <p>Sets the value of the node trace control word to |