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authorSteve Vinoski <[email protected]>2014-01-26 20:34:12 -0500
committerRickard Green <[email protected]>2014-02-24 13:22:31 +0100
commit3e8b423a2cb11f819f3cede7ef817f4012f18944 (patch)
tree7ecb4cffe4bd52343c94eed9acec759bb1b19ad1 /erts/doc/src
parent57573ab98e88ede4b6bca07574e537b6e4f82027 (diff)
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further enhancements for dirty schedulers
Add support for setting the number of dirty CPU schedulers online via erlang:system_flag/2. Assuming the emulator is built with dirty schedulers enabled, the number of dirty CPU schedulers online may not be less than 1, nor greater than the number of dirty CPU schedulers available, nor greater than the number of normal schedulers online. Dirty CPU scheduler threads that are taken offline via system_flag/2 are suspended. The number of dirty CPU schedulers online may be adjusted independently of the number of normal schedulers online, but if system_flag/2 is used to set the number of normal schedulers online to a value less than the current number of normal schedulers online, the number of dirty CPU schedulers online is decreased proportionally. Likewise, if the number of normal schedulers online is increased, the number of dirty CPU schedulers online is increased proportionally. For example, if 8 normal schedulers and 4 dirty CPU schedulers are online, and system_flag/2 is called to set the number of normal schedulers online to 4, the number of dirty CPU schedulers online is also decreased by half, to 2. Subsequently setting the number of normal schedulers online back to 8 also sets the number of dirty CPU schedulers online back to 4. Augment the system_flag/2 documentation in the erlang man page to explain this relationship between schedulers_online and dirty_cpu_schedulers_online. Also ensure that all dirty CPU and I/O schedulers are suspended when multi-scheduling is blocked via system_flag/2, and brought back online when multi-scheduling is unblocked. Add Rickard Green's rewritten check_enqueue_in_prio_queue() function that inspects process state more thoroughly to determine if to enqueue it and if so on what queue, including dirty queues when appropriate. Make sure dirty NIF jobs do not trigger erlang:system_monitor long_schedule messages. Add more dirty scheduler testing to the scheduler test suite. Remove the erts_no_dirty_cpu_schedulers_online global variable, since it's no longer needed. Execute dirty NIFs on a normal scheduler thread while multi-scheduling blocking is in effect. Evacuate any dirty jobs residing in the dirty run queues over to a normal run queue when multi-scheduling is blocked. Allow dirty schedulers to execute aux work. Set the dirty run queues halt_in_progress flag when halting the normal schedulers. Change dirty scheduler numbers to a structure including both scheduler number and type, either dirty CPU or dirty I/O. Add some assertions to ensure that dirty CPU schedulers operate only on dirty CPU scheduler process flags, and the same for dirty I/O schedulers.
Diffstat (limited to 'erts/doc/src')
-rw-r--r--erts/doc/src/erlang.xml33
1 files changed, 25 insertions, 8 deletions
diff --git a/erts/doc/src/erlang.xml b/erts/doc/src/erlang.xml
index 4cf5631727..3004acf124 100644
--- a/erts/doc/src/erlang.xml
+++ b/erts/doc/src/erlang.xml
@@ -5203,9 +5203,16 @@ ok
<c>erlang:system_info(schedulers_online)</c>.
</p>
<p>Returns the old value of the flag.</p>
- <p><em>Note that the dirty schedulers functionality is experimental</em>, and
- that you have to enable support for dirty schedulers when building OTP in
- order to try the functionality out.</p>
+ <p>Note that the number of dirty CPU schedulers online may change if the number of
+ schedulers online changes. For example, if there are 12 schedulers and all are
+ online, and 6 dirty CPU schedulers, all online as well, and <c>system_flag/2</c>
+ is used to set the number of schedulers online to 6, then the number of dirty
+ CPU schedulers online is automatically decreased by half as well, down to 3.
+ Similarly, the number of dirty CPU schedulers online increases proportionally
+ to increases in the number of schedulers online.</p>
+ <p><em>Note that the dirty schedulers functionality is experimental</em>, and
+ that you have to enable support for dirty schedulers when building OTP in order
+ to try out the functionality.</p>
<p>For more information see
<seealso marker="#system_info_dirty_cpu_schedulers">erlang:system_info(dirty_cpu_schedulers)</seealso>
and
@@ -5438,6 +5445,15 @@ ok
<![CDATA[1 <= SchedulersOnline <= erlang:system_info(schedulers)]]>.
</p>
<p>Returns the old value of the flag.</p>
+ <p>Note that if the emulator was built with support for <seealso
+ marker="#system_flag_dirty_cpu_schedulers_online">dirty schedulers</seealso>,
+ changing the number of schedulers online can also change the number of dirty
+ CPU schedulers online. For example, if there are 12 schedulers and all are
+ online, and 6 dirty CPU schedulers, all online as well, and <c>system_flag/2</c>
+ is used to set the number of schedulers online to 6, then the number of dirty
+ CPU schedulers online is automatically decreased by half as well, down to 3.
+ Similarly, the number of dirty CPU schedulers online increases proportionally
+ to increases in the number of schedulers online.</p>
<p>For more information see,
<seealso marker="#system_info_schedulers">erlang:system_info(schedulers)</seealso>,
and
@@ -5817,12 +5833,13 @@ ok
boot time and cannot be changed after that. The number of dirty CPU
scheduler threads online can however be changed at any time. The number of
dirty CPU schedulers can be set on startup by passing
- the <seealso marker="erts:erl#+SDcpu">+SDcpu</seealso> command line flag, see
- <seealso marker="erts:erl#+SDcpu">erl(1)</seealso>.
+ the <seealso marker="erts:erl#+SDcpu">+SDcpu</seealso> or
+ <seealso marker="erts:erl#+SDPcpu">+SDPcpu</seealso> command line flags,
+ see <seealso marker="erts:erl#+SDcpu">erl(1)</seealso>.
</p>
<p><em>Note that the dirty schedulers functionality is experimental</em>, and
that you have to enable support for dirty schedulers when building OTP in
- order to try the functionality out.</p>
+ order to try out the functionality.</p>
<p>See also <seealso marker="#system_flag_dirty_cpu_schedulers_online">erlang:system_flag(dirty_cpu_schedulers_online, DirtyCPUSchedulersOnline)</seealso>,
<seealso marker="#system_info_dirty_cpu_schedulers_online">erlang:system_info(dirty_cpu_schedulers_online)</seealso>,
<seealso marker="#system_info_dirty_io_schedulers">erlang:system_info(dirty_io_schedulers)</seealso>,
@@ -5844,7 +5861,7 @@ ok
</p>
<p><em>Note that the dirty schedulers functionality is experimental</em>, and
that you have to enable support for dirty schedulers when building OTP in
- order to try the functionality out.</p>
+ order to try out the functionality.</p>
<p>For more information, see
<seealso marker="#system_info_dirty_cpu_schedulers">erlang:system_info(dirty_cpu_schedulers)</seealso>,
<seealso marker="#system_info_dirty_io_schedulers">erlang:system_info(dirty_io_schedulers)</seealso>,
@@ -5864,7 +5881,7 @@ ok
</p>
<p><em>Note that the dirty schedulers functionality is experimental</em>, and
that you have to enable support for dirty schedulers when building OTP in
- order to try the functionality out.</p>
+ order to try out the functionality.</p>
<p>For more information, see
<seealso marker="#system_info_dirty_cpu_schedulers">erlang:system_info(dirty_cpu_schedulers)</seealso>,
<seealso marker="#system_info_dirty_cpu_schedulers_online">erlang:system_info(dirty_cpu_schedulers_online)</seealso>, and