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-rw-r--r--erts/doc/src/erlang.xml43
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diff --git a/erts/doc/src/erlang.xml b/erts/doc/src/erlang.xml
index 81e9084e07..14ac97767d 100644
--- a/erts/doc/src/erlang.xml
+++ b/erts/doc/src/erlang.xml
@@ -6038,6 +6038,49 @@ ok
notice.
</p>
</item>
+ <tag><c>{long_schedule, Time}</c></tag>
+ <item>
+ <p>If a process or port in the system runs uninterrupted
+ for at least <c>Time</c> wall clock milliseconds, a
+ message <c>{monitor, PidOrPort, long_schedule, Info}</c>
+ is sent to <c>MonitorPid</c>. <c>PidOrPort</c> is the
+ process or port that was running and <c>Info</c> is a
+ list of two-element tuples describing the event. In case
+ of a <c>pid()</c>, the tuples <c>{timeout, Millis}</c>,
+ <c>{in, Location}</c> and <c>{out, Location}</c> will be
+ present, where <c>Location</c> is either an MFA
+ (<c>{Module, Function, Arity}</c>) describing the
+ function where the process was scheduled in/out, or the
+ atom <c>undefined</c>. In case of a <c>port()</c>, the
+ tuples <c>{timeout, Millis}</c> and <c>{port_op,Op}</c>
+ will be present. <c>Op</c> will be one of <c>proc_sig</c>,
+ <c>timeout</c>, <c>input</c>, <c>output</c>,
+ <c>event</c> or <c>dist_cmd</c>, depending on which
+ driver callback was executing. <c>proc_sig</c> is an
+ internal operation and should never appear, while the
+ others represent the corresponding driver callbacks
+ <c>timeout</c>, <c>ready_input</c>, <c>ready_output</c>,
+ <c>event</c> and finally <c>outputv</c> (when the port
+ is used by distribution). The <c>Millis</c> value in
+ the <c>timeout</c> tuple will tell you the actual
+ uninterrupted execution time of the process or port,
+ which will always be <c>&gt;=</c> the <c>Time</c> value
+ supplied when starting the trace. New tuples may be
+ added to the <c>Info</c> list in the future, and the
+ order of the tuples in the list may be changed at any
+ time without prior notice.
+ </p>
+ <p>This can be used to detect problems with NIF's or
+ drivers that take too long to execute. Generally, 1 ms
+ is considered a good maximum time for a driver callback
+ or a NIF. However, a time sharing system should usually
+ consider everything below 100 ms as "possible" and
+ fairly "normal". Schedule times above that might however
+ indicate swapping or a NIF/driver that is
+ misbehaving. Misbehaving NIF's and drivers could cause
+ bad resource utilization and bad overall performance of
+ the system.</p>
+ </item>
<tag><c>{large_heap, Size}</c></tag>
<item>
<p>If a garbage collection in the system results in