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-rw-r--r--erts/doc/src/erlang.xml313
1 files changed, 295 insertions, 18 deletions
diff --git a/erts/doc/src/erlang.xml b/erts/doc/src/erlang.xml
index 30e6751f41..1f8e89768c 100644
--- a/erts/doc/src/erlang.xml
+++ b/erts/doc/src/erlang.xml
@@ -59,6 +59,12 @@
</datatype>
<datatype>
+ <name name="message_queue_data"></name>
+ <desc><p>See <seealso marker="#process_flag_message_queue_data"><c>erlang:process_flag(message_queue_data, MQD)</c></seealso>.</p>
+ </desc>
+ </datatype>
+
+ <datatype>
<name name="timestamp"></name>
<desc><p>See <seealso marker="#timestamp/0">erlang:timestamp/0</seealso>.</p>
</desc>
@@ -125,6 +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
@@ -1105,7 +1122,7 @@
<fsummary>Prints a term on standard output.</fsummary>
<desc>
<p>Prints a text representation of <c><anno>Term</anno></c> on the
- standard output. On OSE, the term is printed to the ramlog.</p>
+ standard output.</p>
<warning>
<p>This BIF is intended for debugging only.</p>
</warning>
@@ -4281,9 +4298,59 @@ os_prompt% </pre>
<p>Returns the old value of the flag.</p>
</desc>
</func>
-
+ <marker id="process_flag_message_queue_data"/>
<func>
<name name="process_flag" arity="2" clause_i="5"/>
+ <fsummary>Set process flag <c>message_queue_data</c> for the calling process</fsummary>
+ <type name="message_queue_data"/>
+ <desc>
+ <p>This flag determines how messages in the message queue
+ are stored. When the flag is:</p>
+ <taglist>
+ <tag><c>off_heap</c></tag>
+ <item><p>
+ <em>All</em> messages in the message queue will be stored
+ outside of the process heap. This implies that <em>no</em>
+ messages in the message queue will be part of a garbage
+ collection of the process.
+ </p></item>
+ <tag><c>on_heap</c></tag>
+ <item><p>
+ All messages in the message queue will eventually be
+ placed on heap. They may however temporarily be stored
+ off heap. This is how messages always have been stored
+ up until ERTS version 8.0.
+ </p></item>
+ <tag><c>mixed</c></tag>
+ <item><p>
+ Messages may be placed either on the heap or outside
+ of the heap.
+ </p></item>
+ </taglist>
+ <p>
+ The default <c>message_queue_data</c> process flag is determined
+ by the <seealso marker="erl#+xmqd"><c>+xmqd</c></seealso>
+ <c>erl</c> command line argument.
+ </p>
+ <p>
+ If the process potentially may get a hugh amount of messages,
+ you are recommended to set the flag to <c>off_heap</c>. This
+ since a garbage collection with lots of messages placed on
+ the heap may become extremly expensive and the process may
+ consume large amounts of memory. Performance of the
+ actual message passing is however generally better when not
+ using the <c>off_heap</c> flag.
+ </p>
+ <p>
+ When changing this flag messages will be moved. This work
+ has been initiated but not completed when this function
+ call returns.
+ </p>
+ <p>Returns the old value of the flag.</p>
+ </desc>
+ </func>
+ <func>
+ <name name="process_flag" arity="2" clause_i="6"/>
<fsummary>Sets process flag <c>priority</c> for the calling process.</fsummary>
<type name="priority_level"/>
<desc>
@@ -4357,7 +4424,7 @@ os_prompt% </pre>
</func>
<func>
- <name name="process_flag" arity="2" clause_i="6"/>
+ <name name="process_flag" arity="2" clause_i="7"/>
<fsummary>Sets process flag <c>save_calls</c> for the calling process.</fsummary>
<desc>
<p><c><anno>N</anno></c> must be an integer in the interval 0..10000.
@@ -4388,7 +4455,7 @@ os_prompt% </pre>
</func>
<func>
- <name name="process_flag" arity="2" clause_i="7"/>
+ <name name="process_flag" arity="2" clause_i="8"/>
<fsummary>Sets process flag <c>sensitive</c> for the calling process.</fsummary>
<desc>
<p>Sets or clears flag <c>sensitive</c> for the current process.
@@ -4442,6 +4509,7 @@ os_prompt% </pre>
<type name="process_info_result_item"/>
<type name="priority_level"/>
<type name="stack_item"/>
+ <type name="message_queue_data" />
<desc>
<p>Returns a list containing <c><anno>InfoTuple</anno></c>s with
miscellaneous information about the process identified by
@@ -4494,6 +4562,7 @@ os_prompt% </pre>
<type name="process_info_result_item"/>
<type name="stack_item"/>
<type name="priority_level"/>
+ <type name="message_queue_data" />
<desc>
<p>Returns information about the process identified by
<c><anno>Pid</anno></c>, as specified by
@@ -4585,6 +4654,17 @@ os_prompt% </pre>
The content of <c><anno>GCInfo</anno></c> can be changed without
prior notice.</p>
</item>
+ <tag><c>{garbage_collection_info, <anno>GCInfo</anno>}</c></tag>
+ <item>
+ <p><c><anno>GCInfo</anno></c> is a list containing miscellaneous
+ detailed information about garbage collection for this process.
+ The content of <c><anno>GCInfo</anno></c> can be changed without
+ prior notice.
+ See <seealso marker="#gc_start">gc_start</seealso> in
+ <seealso marker="#trace/3">erlang:trace/3</seealso> for details about
+ what each item means.
+ </p>
+ </item>
<tag><c>{group_leader, <anno>GroupLeader</anno>}</c></tag>
<item>
<p><c><anno>GroupLeader</anno></c> is group leader for the I/O of
@@ -4662,6 +4742,15 @@ os_prompt% </pre>
monitor by name, the list item is
<c>{process, {<anno>RegName</anno>, <anno>Node</anno>}}</c>.</p>
</item>
+ <tag><c>{message_queue_data, <anno>MQD</anno>}</c></tag>
+ <item>
+ <p>Returns the current state of the <c>message_queue_data</c>
+ process flag. <c><anno>MQD</anno></c> is either <c>off_heap</c>,
+ <c>on_heap</c>, or <c>mixed</c>. For more information, see the
+ documentation of
+ <seealso marker="#process_flag_message_queue_data"><c>process_flag(message_queue_data,
+ MQD)</c></seealso>.</p>
+ </item>
<tag><c>{priority, <anno>Level</anno>}</c></tag>
<item>
<p><c><anno>Level</anno></c> is the current priority level for
@@ -4804,6 +4893,12 @@ os_prompt% </pre>
<seealso marker="kernel:code">code(3)</seealso>)
and is not to be used elsewhere.</p>
</warning>
+ <note>
+ <p>As from <c>ERTS</c> 8.0 (OTP 19), any lingering processes
+ that still execute the old code will be killed by this function.
+ In earlier versions, such incorrect use could cause much
+ more fatal failures, like emulator crash.</p>
+ </note>
<p>Failure: <c>badarg</c> if there is no old code for
<c><anno>Module</anno></c>.</p>
</desc>
@@ -5430,6 +5525,8 @@ true</pre>
<name name="spawn_opt" arity="2"/>
<fsummary>Creates a new process with a fun as entry point.</fsummary>
<type name="priority_level"/>
+ <type name="message_queue_data" />
+ <type name="spawn_opt_option" />
<desc>
<p>Returns the process identifier (pid) of a new process
started by the application of <c><anno>Fun</anno></c>
@@ -5445,6 +5542,8 @@ true</pre>
<name name="spawn_opt" arity="3"/>
<fsummary>Creates a new process with a fun as entry point on a given node.</fsummary>
<type name="priority_level"/>
+ <type name="message_queue_data" />
+ <type name="spawn_opt_option" />
<desc>
<p>Returns the process identifier (pid) of a new process started
by the application of <c><anno>Fun</anno></c> to the
@@ -5459,6 +5558,8 @@ true</pre>
<name name="spawn_opt" arity="4"/>
<fsummary>Creates a new process with a function as entry point.</fsummary>
<type name="priority_level"/>
+ <type name="message_queue_data" />
+ <type name="spawn_opt_option" />
<desc>
<p>Works as
<seealso marker="#spawn/3">spawn/3</seealso>, except that an
@@ -5560,6 +5661,18 @@ true</pre>
fine-tuning an application and to measure the execution
time with various <c><anno>VSize</anno></c> values.</p>
</item>
+ <tag><c>{message_queue_data, <anno>MQD</anno>}</c></tag>
+ <item>
+ <p>Sets the state of the <c>message_queue_data</c> process
+ flag. <c><anno>MQD</anno></c> should be either <c>off_heap</c>,
+ <c>on_heap</c>, or <c>mixed</c>. The default
+ <c>message_queue_data</c> process flag is determined by the
+ <seealso marker="erl#+xmqd"><c>+xmqd</c></seealso> <c>erl</c>
+ command line argument. For more information, see the
+ documentation of
+ <seealso marker="#process_flag_message_queue_data"><c>process_flag(message_queue_data,
+ <anno>MQD</anno>)</c></seealso>.</p>
+ </item>
</taglist>
</desc>
</func>
@@ -5568,6 +5681,8 @@ true</pre>
<name name="spawn_opt" arity="5"/>
<fsummary>Creates a new process with a function as entry point on a given node.</fsummary>
<type name="priority_level"/>
+ <type name="message_queue_data" />
+ <type name="spawn_opt_option" />
<desc>
<p>Returns the process identifier (pid) of a new process started
by the application
@@ -5756,6 +5871,146 @@ 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>
@@ -5773,7 +6028,7 @@ 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>
@@ -5789,7 +6044,7 @@ 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>
@@ -5809,7 +6064,7 @@ 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>
@@ -5824,7 +6079,7 @@ 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>
@@ -5895,7 +6150,7 @@ 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>
@@ -5913,7 +6168,7 @@ 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>
@@ -5932,7 +6187,7 @@ 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
@@ -6166,6 +6421,17 @@ 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
@@ -6180,7 +6446,7 @@ 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
@@ -6197,7 +6463,7 @@ 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>
@@ -6235,7 +6501,7 @@ 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>
@@ -6353,7 +6619,7 @@ 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>
@@ -6363,7 +6629,7 @@ 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>
@@ -6388,7 +6654,7 @@ 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
@@ -6727,6 +6993,7 @@ ok
<name name="system_info" arity="1" clause_i="65"/>
<name name="system_info" arity="1" clause_i="66"/>
<name name="system_info" arity="1" clause_i="67"/>
+ <name name="system_info" arity="1" clause_i="68"/>
<fsummary>Information about the system.</fsummary>
<desc>
<p>Returns various information about the current system
@@ -7132,7 +7399,17 @@ ok
used by the runtime system. It is on the form
"&lt;major ver&gt;.&lt;minor ver&gt;".</p>
</item>
- <tag><c>otp_release</c></tag>
+ <tag><marker id="system_info_message_queue_data"><c>message_queue_data</c></marker></tag>
+ <item>
+ <p>Returns the default value of the <c>message_queue_data</c>
+ process flag which is either <c>off_heap</c>, <c>on_heap</c>, or <c>mixed</c>.
+ This default is set by the <c>erl</c> command line argument
+ <seealso marker="erl#+xmqd"><c>+xmqd</c></seealso>. For more information on the
+ <c>message_queue_data</c> process flag, see documentation of
+ <seealso marker="#process_flag_message_queue_data"><c>process_flag(message_queue_data,
+ MQD)</c></seealso>.</p>
+ </item>
+ <tag><marker id="system_info_otp_release"><c>otp_release</c></marker></tag>
<item>
<marker id="system_info_otp_release"></marker>
<p>Returns a string containing the OTP release number of the