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-rw-r--r--erts/doc/src/erl.xml50
1 files changed, 39 insertions, 11 deletions
diff --git a/erts/doc/src/erl.xml b/erts/doc/src/erl.xml
index 70569b1c6c..c16b45856d 100644
--- a/erts/doc/src/erl.xml
+++ b/erts/doc/src/erl.xml
@@ -748,19 +748,47 @@
</item>
<tag><marker id="+S"><c><![CDATA[+S Schedulers:SchedulerOnline]]></c></marker></tag>
<item>
- <p>Sets the amount of scheduler threads to create and scheduler
- threads to set online when SMP support has been enabled.
- Valid range for both values are 1-1024. If the
- Erlang runtime system is able to determine the amount
- of logical processors configured and logical processors available,
- <c>Schedulers</c> will default to logical processors configured,
- and <c>SchedulersOnline</c> will default to logical processors
- available; otherwise, the default values will be 1. <c>Schedulers</c>
- may be omitted if <c>:SchedulerOnline</c> is not and vice versa. The
- amount of schedulers online can be changed at run time via
+ <p>Sets the number of scheduler threads to create and scheduler
+ threads to set online when SMP support has been enabled. The maximum for
+ both values is 1024. If the Erlang runtime system is able to determine the
+ amount of logical processors configured and logical processors available,
+ <c>Schedulers</c> will default to logical processors configured, and
+ <c>SchedulersOnline</c> will default to logical processors available;
+ otherwise, the default values will be 1. <c>Schedulers</c> may be omitted
+ if <c>:SchedulerOnline</c> is not and vice versa. The number of schedulers
+ online can be changed at run time via
<seealso marker="erlang#system_flag_schedulers_online">erlang:system_flag(schedulers_online, SchedulersOnline)</seealso>.
</p>
- <p>This flag will be ignored if the emulator doesn't have
+ <p>If <c>Schedulers</c> or <c>SchedulersOnline</c> is specified as a
+ negative number, the value is subtracted from the default number of
+ logical processors configured or logical processors available, respectively.
+ </p>
+ <p>Specifying the value 0 for <c>Schedulers</c> or <c>SchedulersOnline</c>
+ resets the number of scheduler threads or scheduler threads online respectively
+ to its default value.
+ </p>
+ <p>This option is ignored if the emulator doesn't have
+ SMP support enabled (see the <seealso marker="#smp">-smp</seealso>
+ flag).</p>
+ </item>
+ <tag><marker id="+SP"><c><![CDATA[+SP SchedulersPercentage:SchedulersOnlinePercentage]]></c></marker></tag>
+ <item>
+ <p>Similar to <seealso marker="#+S">+S</seealso> but uses percentages to set the
+ number of scheduler threads to create, based on logical processors configured,
+ and scheduler threads to set online, based on logical processors available, when
+ SMP support has been enabled. Specified values must be greater than 0. For example,
+ <c>+SP 50:25</c> sets the number of scheduler threads to 50% of the logical processors
+ configured and the number of scheduler threads online to 25% of the logical processors available.
+ <c>SchedulersPercentage</c> may be omitted if <c>:SchedulersOnlinePercentage</c> is
+ not and vice versa. The number of schedulers online can be changed at run time via
+ <seealso marker="erlang#system_flag_schedulers_online">erlang:system_flag(schedulers_online, SchedulersOnline)</seealso>.
+ </p>
+ <p>This option interacts with <seealso marker="#+S">+S</seealso> settings.
+ For example, on a system with 8 logical cores configured and 8 logical cores
+ available, the combination of the options <c>+S 4:4 +SP 50:25</c> (in either order)
+ results in 2 scheduler threads (50% of 4) and 1 scheduler thread online (25% of 4).
+ </p>
+ <p>This option is ignored if the emulator doesn't have
SMP support enabled (see the <seealso marker="#smp">-smp</seealso>
flag).</p>
</item>