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File 0831-erts-Clarify-system_flag-scheduler_wall_time-_-docs.patch of Package erlang (Revision c43d7e29f1118cfaa3ff5f8a1020d549)

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From 0e3db5dd1eb310519a5b5cd0d2da4acd1dab8177 Mon Sep 17 00:00:00 2001
From: Sverker Eriksson <sverker@erlang.org>
Date: Mon, 22 Nov 2021 23:08:08 +0100
Subject: [PATCH 1/3] erts: Clarify system_flag(scheduler_wall_time,_) docs

---
 erts/doc/src/erlang.xml | 34 ++++++++++++++++++++++++++++++----
 1 file changed, 30 insertions(+), 4 deletions(-)

diff --git a/erts/doc/src/erlang.xml b/erts/doc/src/erlang.xml
index 26f3f768f6..39c2095dc8 100644
--- a/erts/doc/src/erlang.xml
+++ b/erts/doc/src/erlang.xml
@@ -9350,10 +9350,36 @@ ok
 <fsummary>Set system flag scheduler_wall_time.</fsummary>
 <desc>
 
- Turns on or off scheduler wall time measurements.
- For more information, see
- <seeerl marker="#statistics_scheduler_wall_time">
- <c>statistics(scheduler_wall_time)</c></seeerl>.
+ Try enable or disable scheduler wall time measurements by passing
+	 <c><anno>Boolean</anno></c> as either <c>true</c> or <c>false</c>.
+	
+	
+	 For more information about how to use scheduler wall time
+	 measurements, see <seeerl marker="#statistics_scheduler_wall_time">
+ <c>statistics(scheduler_wall_time)</c></seeerl>.
+	
+	
+	 Scheduler wall time measurements has a node global state. It is either
+	 enabled for all processes on the node or disabled for all
+	 processes. Each process has a logical counter initialized as zero. A
+	 call with <c><anno>Boolean</anno></c> as <c>true</c> will increase
+	 that counter one step for the calling process. A call with
+	 <c>false</c> will decrease it one step unless it already is
+	 zero. The node global state for <c>scheduler_wall_time</c> will be
+	 enabled as long as there is at least one process alive with a counter
+	 value larger than zero. When a process terminates, its counter will
+	 also disappear. To ensure <c>scheduler_wall_time</c> is kept enabled,
+	 the process that enabled it must therefore be kept alive.
+	
+	
+	 Returns the old value of the node global state, <c>true</c> if
+	 scheduler wall time measurements were enabled, <c>false</c>
+	 if it were disabled.
+	
+	
+	 Scheduler wall time measurements do consume some cpu overhead and
+	 should not be left turned on unless used.
+	
 </desc>
 </func>
 
-- 
2.31.1

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File 0831-erts-Clarify-system_flag-scheduler_wall_time-_-docs.patch of Package erlang (Revision c43d7e29f1118cfaa3ff5f8a1020d549)

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