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authorRickard Green <[email protected]>2016-06-17 11:53:29 +0200
committerRickard Green <[email protected]>2016-06-17 11:53:29 +0200
commitc9ad0c9fed1d33891f5fa8a4c4511de48417ec10 (patch)
tree791c4c7437ed9323cc3d950933f0ee91ec574699 /erts/doc/src/erl_nif.xml
parent615b79a01706033e1ef0d78f020ebbb47fc80b86 (diff)
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Minor reorganization of dirty NIF documentation
Diffstat (limited to 'erts/doc/src/erl_nif.xml')
-rw-r--r--erts/doc/src/erl_nif.xml55
1 files changed, 29 insertions, 26 deletions
diff --git a/erts/doc/src/erl_nif.xml b/erts/doc/src/erl_nif.xml
index c9b2092c17..f3921f1922 100644
--- a/erts/doc/src/erl_nif.xml
+++ b/erts/doc/src/erl_nif.xml
@@ -385,18 +385,39 @@ ok
<p>
A NIF that cannot be split and cannot execute in a millisecond or
less is called a "dirty NIF" because it performs work that the
- Erlang runtime cannot handle cleanly. Applications that make use
- of such functions must indicate to the runtime that the functions
- are dirty so they can be handled specially. To schedule a dirty
- NIF for execution, the appropriate flags value can be set for the
- NIF in its <seealso marker="#ErlNifFunc"><c>ErlNifFunc</c></seealso>
+ ordinary schedulers of the Erlang runtime system cannot handle cleanly.
+ Applications that make use of such functions must indicate to the
+ runtime that the functions are dirty so they can be handled
+ specially. This is handled by executing dirty jobs on a separate
+ set of schedulers called dirty schedulers. A dirty NIF executing
+ on a dirty scheduler does not have the same duration restriction
+ as a normal NIF.
+ </p>
+
+ <p>
+ It is important to classify the dirty job correct. An I/O bound
+ job should be classified as such, and a CPU bound job should be
+ classified as such. If you should classify CPU bound jobs
+ as I/O bound jobs, dirty I/O schedulers might starve ordinary
+ schedulers. I/O bound jobs are expected to either block waiting
+ for I/O, and/or spend a limited amount of time moving data.
+ </p>
+
+ <p>
+ To schedule a dirty NIF for execution, the appropriate
+ <c>flags</c> value can be set for the NIF in its
+ <seealso marker="#ErlNifFunc"><c>ErlNifFunc</c></seealso>
entry, or the application can call
<seealso marker="#enif_schedule_nif"><c>enif_schedule_nif</c></seealso>,
passing to it a pointer to the dirty NIF to be executed and
indicating with the <c>flags</c> argument whether it expects the
- operation to be CPU-bound or I/O-bound. A dirty NIF executing
- on a dirty scheduler does not have the same duration restriction
- as a normal NIF.
+ operation to be CPU-bound or I/O-bound. A job that alternates
+ between I/O bound and CPU bound can be reclassified and
+ rescheduled using <c>enif_schedule_nif</c> so that it executes on
+ the correct type of dirty scheduler at all times. For more
+ information see the documentation of the <c>erl</c> command line
+ arguments <seealso marker="erl#+SDcpu"><c>+SDcpu</c></seealso>,
+ and <seealso marker="erl#+SDio"><c>+SDio</c></seealso>.
</p>
<p>
@@ -442,24 +463,6 @@ ok
dirty NIF has completed.
</p>
- <p>
- It is important to classify the dirty job correct. An I/O bound
- job should be classified as such and execute on a dirty I/O
- scheduler, and a CPU bound job should be classified as such and
- execute on a dirty CPU scheduler. If you classify CPU bound jobs
- as I/O bound jobs, dirty I/O schedulers might starve ordinary
- schedulers. For more information see the documentation
- of the <c>erl</c> command line arguments
- <seealso marker="erl#+SDcpu"><c>+SDcpu</c></seealso>, and
- <seealso marker="erl#+SDio"><c>+SDio</c></seealso> as well
- as <seealso marker="#enif_schedule_nif"><c>enif_schedule_nif</c></seealso>,
- and <seealso marker="#ErlNifFunc"><c>ErlNifFunc</c></seealso>.
- A job that alternates between I/O bound and CPU bound can
- be reclassified and rescheduled using <c>enif_schedule_nif</c>
- so that it exectutes on the correct type of dirty scheduler
- at all times.
- </p>
-
<p>Currently known issues that are planned to be fixed:</p>
<list>
<item>