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-rw-r--r--erts/doc/src/erlang.xml114
1 files changed, 109 insertions, 5 deletions
diff --git a/erts/doc/src/erlang.xml b/erts/doc/src/erlang.xml
index 13b16d1ed3..c3e2ed61e9 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>
@@ -1105,7 +1111,7 @@
<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>
@@ -4280,9 +4286,59 @@ 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>
@@ -4356,7 +4412,7 @@ 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.
@@ -4387,7 +4443,7 @@ 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.
@@ -4441,6 +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
@@ -4493,6 +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
@@ -4661,6 +4719,15 @@ 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
@@ -4803,6 +4870,12 @@ 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>
@@ -5429,6 +5502,8 @@ 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>
@@ -5444,6 +5519,8 @@ 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
@@ -5458,6 +5535,8 @@ 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
@@ -5559,6 +5638,18 @@ 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>
@@ -5567,6 +5658,8 @@ 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
@@ -6726,6 +6819,7 @@ 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
@@ -7131,7 +7225,17 @@ 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