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-rw-r--r--erts/doc/src/erlang.xml94
1 files changed, 60 insertions, 34 deletions
diff --git a/erts/doc/src/erlang.xml b/erts/doc/src/erlang.xml
index 2e82bb62a9..6ed03f3dfc 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>
@@ -4280,39 +4286,52 @@ os_prompt% </pre>
<p>Returns the old value of the flag.</p>
</desc>
</func>
- <marker id="process_flag_off_heap_message_queue"/>
+ <marker id="process_flag_message_queue_data"/>
<func>
<name name="process_flag" arity="2" clause_i="5"/>
- <fsummary>Set process flag <c>off_heap_message_queue</c> for the calling process</fsummary>
+ <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>true</c></tag>
+ <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>false</c></tag>
+ <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>true</c>. This since
- a garbage collection with lots of messages placed on the heap
- may become extremly expensive. Performance of the actual
- message passing is however generally better when setting the
- flag to <c>false</c>.
+ 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 from <c>false</c> to <c>true</c>,
- all messages in the message queue are moved off heap. This
- work has been initiated but not completed when this function
+ 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>
@@ -4478,6 +4497,7 @@ 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
@@ -4530,6 +4550,7 @@ 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
@@ -4698,13 +4719,14 @@ os_prompt% </pre>
monitor by name, the list item is
<c>{process, {<anno>RegName</anno>, <anno>Node</anno>}}</c>.</p>
</item>
- <tag><c>{off_heap_message_queue, <anno>OHMQ</anno>}</c></tag>
+ <tag><c>{message_queue_data, <anno>MQD</anno>}</c></tag>
<item>
- <p>Returns the current state of the <c>off_heap_message_queue</c>
- process flag. <c><anno>OHMQ</anno></c> is either <c>true</c>, or
- <c>false</c>. For more information, see the documentation of
- <seealso marker="#process_flag_off_heap_message_queue"><c>process_flag(off_heap_message_queue,
- OHMQ)</c></seealso>.</p>
+ <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>
@@ -5474,6 +5496,7 @@ 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
@@ -5490,6 +5513,7 @@ 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
@@ -5505,6 +5529,7 @@ 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
@@ -5607,17 +5632,17 @@ true</pre>
fine-tuning an application and to measure the execution
time with various <c><anno>VSize</anno></c> values.</p>
</item>
- <tag><c>{off_heap_message_queue, <anno>OHMQ</anno>}</c></tag>
+ <tag><c>{message_queue_data, <anno>MQD</anno>}</c></tag>
<item>
- <p>Sets the state of the <c>off_heap_message_queue</c> process
- flag. <c><anno>OHMQ</anno></c> should be either <c>true</c>, or
- <c>false</c>. The default <c>off_heap_message_queue</c> process
- flag is determined by the
- <seealso marker="erl#+xohmq"><c>+xohmq</c></seealso> <c>erl</c>
+ <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_off_heap_message_queue"><c>process_flag(off_heap_message_queue,
- <anno>OHMQ</anno>)</c></seealso>.</p>
+ <seealso marker="#process_flag_message_queue_data"><c>process_flag(message_queue_data,
+ <anno>MQD</anno>)</c></seealso>.</p>
</item>
</taglist>
</desc>
@@ -5627,6 +5652,7 @@ 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
@@ -7106,15 +7132,15 @@ ok
used by the runtime system. It is on the form
"&lt;major ver&gt;.&lt;minor ver&gt;".</p>
</item>
- <tag><marker id="system_info_off_heap_message_queue"><c>off_heap_message_queue</c></marker></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>off_heap_message_queue</c>
- process flag which is either <c>true</c> or <c>false</c>. This
- default is set by the <c>erl</c> command line argument
- <seealso marker="erl#+xohmq"><c>+xohmq</c></seealso>. For more information on the
- <c>off_heap_message_queue</c> process flag, see documentation of
- <seealso marker="#process_flag_off_heap_message_queue"><c>process_flag(off_heap_message_queue,
- OHMQ)</c></seealso>.</p>
+ <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>