File 3501-runtime_tools-Clarify-scheduler-docs.patch of Package erlang

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File 3501-runtime_tools-Clarify-scheduler-docs.patch of Package erlang (Revision a158bff6d0635105e5353db4b3451ab1)

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From d9814796e4a735e4a452a11389359b1c503814b5 Mon Sep 17 00:00:00 2001
From: Sverker Eriksson <sverker@erlang.org>
Date: Thu, 18 Feb 2021 13:38:26 +0100
Subject: [PATCH] runtime_tools: Clarify scheduler docs
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Co-authored-by: José Valim <jose.valim@gmail.com>
Co-authored-by: Paulo F. Oliveira <paulo.ferraz.oliveira@gmail.com>
---
 lib/runtime_tools/doc/src/scheduler.xml | 28 ++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/lib/runtime_tools/doc/src/scheduler.xml b/lib/runtime_tools/doc/src/scheduler.xml
index 713d70548b..d539ccb1c6 100644
--- a/lib/runtime_tools/doc/src/scheduler.xml
+++ b/lib/runtime_tools/doc/src/scheduler.xml
@@ -63,7 +63,10 @@
 	<taglist>
 	 <tag><c>{normal, SchedulerId, Util, Percent}</c></tag>
 	 <item>Scheduler utilization of a normal scheduler with number
-	 <c>SchedulerId</c>.</item>
+	 <c>SchedulerId</c>. Schedulers that are not online will also be
+	 included.
+	 <seealso marker="erts:erlang#system_info_schedulers_online">Online
+	 schedulers</seealso> have the lowest <c>SchedulerId</c>.</item>
 	 <tag><c>{cpu, SchedulerId, Util, Percent}</c></tag>
 	 <item>Scheduler utilization of a dirty-cpu scheduler with number
 	 <c>SchedulerId</c>.</item>
@@ -117,6 +120,29 @@
 Calculate scheduler utilizations for the time interval from when
 	<c><anno>Sample</anno></c> was taken and "now". The same as calling
 	<c>scheduler:utilization(Sample, scheduler:sample_all())</c>.
+	<note>
+	 
+	 Scheduler utilization is measured as an average value over a time
+	 interval, calculated as the difference between two samples. To get
+	 good useful utilization values at least a couple of seconds should
+	 have passed between the two samples. For this reason, you should not
+	 do
+	 
+<pre>
+scheduler:utilization(scheduler:sample()). % DO NOT DO THIS!
+</pre>
+ 
+ The above example takes two samples in rapid succession and calculates
+	 the scheduler utilization between them. The resulting values will
+	 probably be more misleading than informative.
+	 
+	 
+	 Instead use <seealso marker="#utilization/1">
+	 <c>scheduler:utilization(Seconds)</c></seealso> or let some time pass
+	 between <c>Sample=scheduler:sample()</c> and
+	 <c>scheduler:utilization(Sample)</c>.
+	 
+	</note>
 </desc>
 </func>
 
-- 
2.26.2

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File 3501-runtime_tools-Clarify-scheduler-docs.patch of Package erlang (Revision a158bff6d0635105e5353db4b3451ab1)

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