diff options
| author | Sebastian Huber <sebastian.huber@embedded-brains.de> | 2018-10-20 19:30:42 +0200 |
|---|---|---|
| committer | Sebastian Huber <sebastian.huber@embedded-brains.de> | 2018-10-26 19:11:45 +0200 |
| commit | 955d36640fbe939c430540e0ed52ef59c04ceac0 (patch) | |
| tree | eac950eb1ba7f724686b50e6abe953999b222717 /c-user/scheduling_concepts.rst | |
| parent | Add a README file containing the colours used in the RTEMS logo. (diff) | |
| download | rtems-docs-955d36640fbe939c430540e0ed52ef59c04ceac0.tar.bz2 | |
c-user: Clarify scheduler configuration
Diffstat (limited to 'c-user/scheduling_concepts.rst')
| -rw-r--r-- | c-user/scheduling_concepts.rst | 35 |
1 files changed, 21 insertions, 14 deletions
diff --git a/c-user/scheduling_concepts.rst b/c-user/scheduling_concepts.rst index 239e0c3..e088c62 100644 --- a/c-user/scheduling_concepts.rst +++ b/c-user/scheduling_concepts.rst @@ -239,20 +239,27 @@ allowed to run. Earliest Deadline First SMP Scheduler ------------------------------------- -A job-level fixed-priority scheduler using the Earliest Deadline First (EDF) -method. By convention, the maximum priority level is -:math:`min(INT\_MAX, 2^{62} - 1)` for background tasks. The tasks with an -active deadline have a higher priority than the background tasks. This -scheduler supports task processor affinities of one-to-one and one-to-all, e.g. -a task can execute on exactly one processor or all processors managed by the -scheduler instance. This is the default scheduler in SMP configurations if -more than one processor is configured. The processor affinity set of a task -must contain all online processors to select the one-to-all affinity. This is -to avoid pathological cases if processors are added/removed to/from the -scheduler instance at run-time. In case the processor affinity set contains -not all online processors, then a one-to-one affinity will be used selecting -the processor with the largest index within the set of processors currently -owned by the scheduler instance. +This is a job-level fixed-priority scheduler using the Earliest Deadline First +(EDF) method. By convention, the maximum priority level is +:math:`min(INT\_MAX, 2^{62} - 1)` for background tasks. Tasks without an +active deadline are background tasks. In case deadlines are not used, then the +EDF scheduler behaves exactly like a fixed-priority scheduler. The tasks with +an active deadline have a higher priority than the background tasks. This +scheduler supports :ref:`task processor affinities <rtems_task_set_affinity>` +of one-to-one and one-to-all, e.g. a task can execute on exactly one processor +or all processors managed by the scheduler instance. The processor affinity +set of a task must contain all online processors to select the one-to-all +affinity. This is to avoid pathological cases if processors are added/removed +to/from the scheduler instance at run-time. In case the processor affinity set +contains not all online processors, then a one-to-one affinity will be used +selecting the processor with the largest index within the set of processors +currently owned by the scheduler instance. This scheduler algorithm supports +:ref:`thread pinning <ThreadPinning>`. The ready queues use a red-black tree +with the task priority as the key. + +This scheduler algorithm is the default scheduler in SMP configurations if more +than one processor is configured (:ref:`CONFIGURE_MAXIMUM_PROCESSORS +<CONFIGURE_MAXIMUM_PROCESSORS>`). .. _SchedulerSMPPriority: |