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authorRickard Green <[email protected]>2011-12-01 09:47:25 +0100
committerRickard Green <[email protected]>2011-12-01 09:47:25 +0100
commitf597c0d9de1e8f7ffec0d63e07a6ae85eae3cd27 (patch)
treeccb2e9db5de897a115a8f8746766234c731b47a4 /erts/doc/src/erl.xml
parent736bd3aa619244786c32c882001604210f846fa4 (diff)
parentd4f67bb08dec687671929b389f172dc2988aa363 (diff)
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Merge branch 'rickard/deprecate-runtime-binding/OTP-9749'
* rickard/deprecate-runtime-binding/OTP-9749: Deprecate erlang:system_flag/2 arguments scheduler_bind_type and cpu_topology
Diffstat (limited to 'erts/doc/src/erl.xml')
-rw-r--r--erts/doc/src/erl.xml105
1 files changed, 75 insertions, 30 deletions
diff --git a/erts/doc/src/erl.xml b/erts/doc/src/erl.xml
index 53f46d2a2e..9fb718e60f 100644
--- a/erts/doc/src/erl.xml
+++ b/erts/doc/src/erl.xml
@@ -665,41 +665,66 @@
</p>
<taglist>
<tag><c>u</c></tag>
- <item><p>Same as
- <seealso marker="erlang#system_flag_scheduler_bind_type">erlang:system_flag(scheduler_bind_type, unbound)</seealso>.
- </p></item>
+ <item>
+ <p><c>unbound</c> - Schedulers will not be bound to logical
+ processors, i.e., the operating system decides where the
+ scheduler threads execute, and when to migrate them. This is
+ the default.</p>
+ </item>
<tag><c>ns</c></tag>
- <item><p>Same as
- <seealso marker="erlang#system_flag_scheduler_bind_type">erlang:system_flag(scheduler_bind_type, no_spread)</seealso>.
- </p></item>
+ <item>
+ <p><c>no_spread</c> - Schedulers with close scheduler
+ identifiers will be bound as close as possible in hardware.</p>
+ </item>
<tag><c>ts</c></tag>
- <item><p>Same as
- <seealso marker="erlang#system_flag_scheduler_bind_type">erlang:system_flag(scheduler_bind_type, thread_spread)</seealso>.
- </p></item>
+ <item>
+ <p><c>thread_spread</c> - Thread refers to hardware threads
+ (e.g. Intels hyper-threads). Schedulers with low scheduler
+ identifiers, will be bound to the first hardware thread of
+ each core, then schedulers with higher scheduler identifiers
+ will be bound to the second hardware thread of each core,
+ etc.</p>
+ </item>
<tag><c>ps</c></tag>
- <item><p>Same as
- <seealso marker="erlang#system_flag_scheduler_bind_type">erlang:system_flag(scheduler_bind_type, processor_spread)</seealso>.
- </p></item>
+ <item>
+ <p><c>processor_spread</c> - Schedulers will be spread like
+ <c>thread_spread</c>, but also over physical processor chips.</p>
+ </item>
<tag><c>s</c></tag>
- <item><p>Same as
- <seealso marker="erlang#system_flag_scheduler_bind_type">erlang:system_flag(scheduler_bind_type, spread)</seealso>.
- </p></item>
+ <item>
+ <p><c>spread</c> - Schedulers will be spread as much as
+ possible.</p>
+ </item>
<tag><c>nnts</c></tag>
- <item><p>Same as
- <seealso marker="erlang#system_flag_scheduler_bind_type">erlang:system_flag(scheduler_bind_type, no_node_thread_spread)</seealso>.
- </p></item>
+ <item>
+ <p><c>no_node_thread_spread</c> - Like <c>thread_spread</c>,
+ but if multiple NUMA (Non-Uniform Memory Access) nodes exists,
+ schedulers will be spread over one NUMA node at a time,
+ i.e., all logical processors of one NUMA node will be bound
+ to schedulers in sequence.</p>
+ </item>
<tag><c>nnps</c></tag>
- <item><p>Same as
- <seealso marker="erlang#system_flag_scheduler_bind_type">erlang:system_flag(scheduler_bind_type, no_node_processor_spread)</seealso>.
- </p></item>
+ <item>
+ <p><c>no_node_processor_spread</c> - Like
+ <c>processor_spread</c>, but if multiple NUMA nodes exists,
+ schedulers will be spread over one NUMA node at a time, i.e.,
+ all logical processors of one NUMA node will be bound to
+ schedulers in sequence.</p>
+ </item>
<tag><c>tnnps</c></tag>
- <item><p>Same as
- <seealso marker="erlang#system_flag_scheduler_bind_type">erlang:system_flag(scheduler_bind_type, thread_no_node_processor_spread)</seealso>.
- </p></item>
+ <item>
+ <p><c>thread_no_node_processor_spread</c> - A combination of
+ <c>thread_spread</c>, and <c>no_node_processor_spread</c>.
+ Schedulers will be spread over hardware threads across NUMA
+ nodes, but schedulers will only be spread over processors
+ internally in one NUMA node at a time.</p>
+ </item>
<tag><c>db</c></tag>
- <item><p>Same as
- <seealso marker="erlang#system_flag_scheduler_bind_type">erlang:system_flag(scheduler_bind_type, default_bind)</seealso>.
- </p></item>
+ <item>
+ <p><c>default_bind</c> - Binds schedulers the default way.
+ Currently the default is <c>thread_no_node_processor_spread</c>
+ (which might change in the future).</p>
+ </item>
</taglist>
<p>Binding of schedulers is currently only supported on newer
Linux, Solaris, FreeBSD, and Windows systems.</p>
@@ -723,8 +748,22 @@
instead. In some cases this performance penalty might be
severe. If this is the case, you are advised to not
bind the schedulers.</p>
- <p>For more information, see
- <seealso marker="erlang#system_flag_scheduler_bind_type">erlang:system_flag(scheduler_bind_type, SchedulerBindType)</seealso>.
+ <p>How schedulers are bound matters. For example, in
+ situations when there are fewer running processes than
+ schedulers online, the runtime system tries to migrate
+ processes to schedulers with low scheduler identifiers.
+ The more the schedulers are spread over the hardware,
+ the more resources will be available to the runtime
+ system in such situations.
+ </p>
+ <p>
+ <em>NOTE:</em> If a scheduler fails to bind, this
+ will often be silently ignored. This since it isn't always
+ possible to verify valid logical processor identifiers. If
+ an error is reported, it will be reported to the
+ <c>error_logger</c>. If you want to verify that the
+ schedulers actually have bound as requested, call
+ <seealso marker="erlang#system_info_scheduler_bindings">erlang:system_info(scheduler_bindings)</seealso>.
</p>
</item>
<tag><marker id="+scl"><c>+scl true|false</c></marker></tag>
@@ -755,6 +794,12 @@
<item><c><![CDATA[<IdDefs> = <LogicalIds><ThreadIds><CoreIds><ProcessorIds><NodeIds> | <LogicalIds><ThreadIds><CoreIds><NodeIds><ProcessorIds>]]></c></item>
<item><c><![CDATA[CpuTopology = <IdDefs>:<IdDefs> | <IdDefs>]]></c></item>
</list>
+ <p>Set a user defined CPU topolgy. The user defined
+ CPU topology will override any automatically detected
+ CPU topology. The CPU topology is used when
+ <seealso marker="#+sbt">binding schedulers to logical
+ processors</seealso>.
+ </p>
<p>Upper-case letters signify real identifiers and lower-case
letters signify fake identifiers only used for description
of the topology. Identifiers passed as real identifiers may
@@ -854,7 +899,7 @@
how the real CPU topology looks like is likely to
decrease the performance of the runtime system.</p>
<p>For more information, see
- <seealso marker="erlang#system_flag_cpu_topology">erlang:system_flag(cpu_topology, CpuTopology)</seealso>.</p>
+ <seealso marker="erlang#system_info_cpu_topology">erlang:system_info(cpu_topology)</seealso>.</p>
</item>
<tag><marker id="+swt"><c>+swt very_low|low|medium|high|very_high</c></marker></tag>
<item>