diff options
Diffstat (limited to 'erts')
| -rw-r--r-- | erts/doc/src/erl.xml | 19 | ||||
| -rw-r--r-- | erts/doc/src/erl_nif.xml | 20 |
2 files changed, 37 insertions, 2 deletions
diff --git a/erts/doc/src/erl.xml b/erts/doc/src/erl.xml index 7b90a1ccca..436c2c57e1 100644 --- a/erts/doc/src/erl.xml +++ b/erts/doc/src/erl.xml @@ -915,6 +915,13 @@ number of dirty CPU schedulers online can be changed at run time via <seealso marker="erlang#system_flag_dirty_cpu_schedulers_online">erlang:system_flag(dirty_cpu_schedulers_online, DirtyCPUSchedulersOnline)</seealso>. </p> + <p> + The amount of dirty CPU schedulers is limited by the amount of + normal schedulers in order to limit the effect on processes + executing on ordinary schedulers. If the amount of dirty CPU + schedulers was allowed to be unlimited, dirty CPU bound jobs would + potentially starve normal jobs. + </p> <p>This option is ignored if the emulator doesn't have threading support enabled. Currently, <em>this option is experimental</em> and is supported only if the emulator was configured and built with support for dirty schedulers @@ -944,7 +951,7 @@ enabled (it's disabled by default). </p> </item> - <tag><marker id="+SDio"/><c><![CDATA[+SDio IOSchedulers]]></c></tag> + <tag><marker id="+SDio"/><c><![CDATA[+SDio DirtyIOSchedulers]]></c></tag> <item> <p>Sets the number of dirty I/O scheduler threads to create when threading support has been enabled. The valid range is 0-1024. By default, the number @@ -952,6 +959,16 @@ threads in the <seealso marker="#async_thread_pool_size">async thread pool </seealso>. </p> + <p> + The amount of dirty IO schedulers is not limited by the amount of + normal schedulers <seealso marker="#+SDcpu">like the amount of + dirty CPU schedulers</seealso>. This since only I/O bound work is + expected to execute on dirty I/O schedulers. I/O bound jobs are + expected to either block waiting for I/O, and/or spend a limited + amount of time moving data. However, if the user should schedule CPU + bound jobs on dirty I/O schedulers, these jobs might starve ordinary + jobs executing on ordinary schedulers. + </p> <p>This option is ignored if the emulator doesn't have threading support enabled. Currently, <em>this option is experimental</em> and is supported only if the emulator was configured and built with support for dirty schedulers diff --git a/erts/doc/src/erl_nif.xml b/erts/doc/src/erl_nif.xml index 8b02b3bae1..c9b2092c17 100644 --- a/erts/doc/src/erl_nif.xml +++ b/erts/doc/src/erl_nif.xml @@ -442,6 +442,24 @@ 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> @@ -1702,7 +1720,7 @@ enif_map_iterator_destroy(env, &iter); be converted to an atom, <c>enif_schedule_nif</c> returns a <c>badarg</c> exception.</p> <p>The <c>flags</c> argument must be set to 0 for a regular NIF, or if the emulator was built the experimental dirty scheduler support enabled, <c>flags</c> can be set to either <c>ERL_NIF_DIRTY_JOB_CPU_BOUND</c> - if the job is expected to be primarily CPU-bound, or <c>ERL_NIF_DIRTY_JOB_IO_BOUND</c> for jobs that will + if the job is expected to be CPU-bound, or <c>ERL_NIF_DIRTY_JOB_IO_BOUND</c> for jobs that will be I/O-bound. If dirty scheduler threads are not available in the emulator, a try to schedule such a job will result in a <c>badarg</c> exception.</p> |