[rtems-docs commit] c-user: Rework scheduler alogrithm config defs
Sebastian Huber
sebh at rtems.org
Thu Mar 8 06:47:29 UTC 2018
Module: rtems-docs
Branch: master
Commit: bf78123adaaef8e56eb76e5d6bf9c0ba1b03b57e
Changeset: http://git.rtems.org/rtems-docs/commit/?id=bf78123adaaef8e56eb76e5d6bf9c0ba1b03b57e
Author: Sebastian Huber <sebastian.huber at embedded-brains.de>
Date: Thu Mar 8 07:44:08 2018 +0100
c-user: Rework scheduler alogrithm config defs
Update #3325.
---
c-user/configuring_a_system.rst | 170 ++++++++++++++++++++++------------------
1 file changed, 92 insertions(+), 78 deletions(-)
diff --git a/c-user/configuring_a_system.rst b/c-user/configuring_a_system.rst
index 2d38aa4..58b381c 100644
--- a/c-user/configuring_a_system.rst
+++ b/c-user/configuring_a_system.rst
@@ -3326,17 +3326,13 @@ DEFAULT VALUE:
This is not defined by default.
DESCRIPTION:
- The Constant Bandwidth Server Scheduler (CBS) is an alternative scheduler
- in RTEMS for uniprocessor applications. The CBS is a budget aware
- extension of EDF scheduler. The goal of this scheduler is to ensure
- temporal isolation of tasks. The CBS is equipped with a set of additional
- rules and provides with an extensive API.
-
- This scheduler may be explicitly selected by defining
- ``CONFIGURE_SCHEDULER_CBS``.
+ If defined, then the :ref:`Constant Bandwidth Server (CBS) Scheduler
+ <SchedulerCBS>` algorithm is made available to the application.
NOTES:
- None.
+ In case no explicit :ref:`clustered scheduler configuration
+ <ConfigurationSchedulersClustered>` is present, then it is used as the
+ scheduler for exactly one processor.
.. index:: CONFIGURE_SCHEDULER_EDF
@@ -3358,21 +3354,13 @@ DEFAULT VALUE:
This is not defined by default.
DESCRIPTION:
- The Earliest Deadline First Scheduler (EDF) is an alternative scheduler in
- RTEMS for uniprocessor applications. The EDF schedules tasks with dynamic
- priorities equal to deadlines. The deadlines are declared using only Rate
- Monotonic manager which handles periodic behavior. Period is always equal
- to deadline. If a task does not have any deadline declared or the deadline
- is cancelled, the task is considered a background task which is scheduled
- in case no deadline-driven tasks are ready to run. Moreover, multiple
- background tasks are scheduled according their priority assigned upon
- initialization. All ready tasks reside in a single ready queue.
-
- This scheduler may be explicitly selected by defining
- ``CONFIGURE_SCHEDULER_EDF``.
+ If defined, then the :ref:`Earliest Deadline First (EDF) Scheduler
+ <SchedulerEDF>` algorithm is made available to the application.
NOTES:
- None.
+ In case no explicit :ref:`clustered scheduler configuration
+ <ConfigurationSchedulersClustered>` is present, then it is used as the
+ scheduler for exactly one processor.
.. index:: CONFIGURE_SCHEDULER_EDF_SMP
@@ -3394,11 +3382,20 @@ DEFAULT VALUE:
This is not defined by default.
DESCRIPTION:
- If defined, then the Earliest Deadline First (EDF) SMP Scheduler is
- selected as the default scheduler.
+ If defined, then the :ref:`Earliest Deadline First (EDF) SMP Scheduler
+ <SchedulerSMPEDF>` algorithm is made available to the application.
NOTES:
- None.
+ This scheduler algorithm is only available when RTEMS is built with SMP
+ support enabled.
+
+ In case no explicit :ref:`clustered scheduler configuration
+ <ConfigurationSchedulersClustered>` is present, then it is used as the
+ scheduler for up to 32 processors.
+
+ This scheduler algorithm is the default in SMP configurations and is only
+ selected when :ref:`CONFIGURE_MAXIMUM_PROCESSORS
+ <CONFIGURE_MAXIMUM_PROCESSORS>` is greater than one.
.. index:: CONFIGURE_SCHEDULER_NAME
@@ -3456,16 +3453,49 @@ DEFAULT VALUE:
this configuration parameter is redundant.
DESCRIPTION:
- The Deterministic Priority Scheduler is the default scheduler in RTEMS for
- uniprocessor applications and is designed for predictable performance
- under the highest loads. It can block or unblock a thread in a constant
- amount of time. This scheduler requires a variable amount of memory based
- upon the number of priorities configured in the system.
+ If defined, then the :ref:`Deterministic Priority Scheduler
+ <SchedulerPriority>` algorithm is made available to the application.
NOTES:
- This scheduler may be explicitly selected by defining
- ``CONFIGURE_SCHEDULER_PRIORITY`` although this is equivalent to the default
- behavior.
+ In case no explicit :ref:`clustered scheduler configuration
+ <ConfigurationSchedulersClustered>` is present, then it is used as the
+ scheduler for exactly one processor.
+
+ This scheduler algorithm is the default when
+ :ref:`CONFIGURE_MAXIMUM_PROCESSORS <CONFIGURE_MAXIMUM_PROCESSORS>` is
+ exactly one.
+
+.. index:: CONFIGURE_SCHEDULER_PRIORITY_AFFINITY_SMP
+
+.. _CONFIGURE_SCHEDULER_PRIORITY_AFFINITY_SMP:
+
+CONFIGURE_SCHEDULER_PRIORITY_AFFINITY_SMP
+-----------------------------------------
+
+CONSTANT:
+ ``CONFIGURE_SCHEDULER_PRIORITY_AFFINITY_SMP``
+
+DATA TYPE:
+ Boolean feature macro.
+
+RANGE:
+ Defined or undefined.
+
+DEFAULT VALUE:
+ This is not defined by default.
+
+DESCRIPTION:
+ If defined, then the :ref:`Arbitrary Processor Affinity SMP Scheduler
+ <SchedulerSMPPriorityAffinity>` algorithm is made available to the
+ application.
+
+NOTES:
+ This scheduler algorithm is only available when RTEMS is built with SMP
+ support enabled.
+
+ In case no explicit :ref:`clustered scheduler configuration
+ <ConfigurationSchedulersClustered>` is present, then it is used as the
+ scheduler for up to 32 processors.
.. index:: CONFIGURE_SCHEDULER_PRIORITY_SMP
@@ -3487,19 +3517,16 @@ DEFAULT VALUE:
This is not defined by default.
DESCRIPTION:
- The Deterministic Priority SMP Scheduler is derived from the Deterministic
- Priority Scheduler but is capable of scheduling threads across multiple
- processors.
-
- In a configuration with SMP enabled at configure time, it may be explicitly
- selected by defining ``CONFIGURE_SCHEDULER_PRIORITY_SMP``.
+ If defined, then the :ref:`Deterministic Priority SMP Scheduler
+ <SchedulerSMPPriority>` algorithm is made available to the application.
NOTES:
- This scheduler is only available when RTEMS is configured with SMP support
- enabled.
+ This scheduler algorithm is only available when RTEMS is built with SMP
+ support enabled.
- This scheduler is currently the default in SMP configurations and is only
- selected when ``CONFIGURE_MAXIMUM_PROCESSORS`` is greater than one.
+ In case no explicit :ref:`clustered scheduler configuration
+ <ConfigurationSchedulersClustered>` is present, then it is used as the
+ scheduler for up to 32 processors.
.. index:: CONFIGURE_SCHEDULER_SIMPLE
@@ -3521,19 +3548,13 @@ DEFAULT VALUE:
This is not defined by default.
DESCRIPTION:
- When defined, the Simple Priority Scheduler is used at the thread
- scheduling algorithm. This is an alternative scheduler in RTEMS. It is
- designed to provide the same task scheduling behaviour as the Deterministic
- Priority Scheduler while being simpler in implementation and uses less
- memory for data management. It maintains a single sorted list of all ready
- threads. Thus blocking or unblocking a thread is not a constant time
- operation with this scheduler.
-
- This scheduler may be explicitly selected by defining
- ``CONFIGURE_SCHEDULER_SIMPLE``.
+ If defined, then the :ref:`Simple Priority Scheduler
+ <SchedulerPrioritySimple>` algorithm is made available to the application.
NOTES:
- This scheduler is appropriate for use in small systems where RAM is limited.
+ In case no explicit :ref:`clustered scheduler configuration
+ <ConfigurationSchedulersClustered>` is present, then it is used as the
+ scheduler for exactly one processor.
.. index:: CONFIGURE_SCHEDULER_SIMPLE_SMP
@@ -3555,25 +3576,17 @@ DEFAULT VALUE:
This is not defined by default.
DESCRIPTION:
- The Simple SMP Priority Scheduler is derived from the Simple Priority
- Scheduler but is capable of scheduling threads across multiple processors.
- It is designed to provide the same task scheduling behaviour as the
- Deterministic Priority Scheduler while distributing threads across multiple
- processors. Being based upon the Simple Priority Scheduler, it also
- maintains a single sorted list of all ready threads. Thus blocking or
- unblocking a thread is not a constant time operation with this scheduler.
-
- In addition, when allocating threads to processors, the algorithm is not
- constant time. This algorithm was not designed with efficiency as a primary
- design goal. Its primary design goal was to provide an SMP-aware
- scheduling algorithm that is simple to understand.
-
- In a configuration with SMP enabled at configure time, it may be explicitly
- selected by defining ``CONFIGURE_SCHEDULER_SIMPLE_SMP``.
+ If defined, then the :ref:`Simple Priority SMP Scheduler
+ <SchedulerSMPPrioritySimple>` algorithm is made available to the
+ application.
NOTES:
- This scheduler is only available when RTEMS is configured with SMP support
- enabled.
+ This scheduler algorithm is only available when RTEMS is built with SMP
+ support enabled.
+
+ In case no explicit :ref:`clustered scheduler configuration
+ <ConfigurationSchedulersClustered>` is present, then it is used as the
+ scheduler for up to 32 processors.
.. index:: CONFIGURE_SCHEDULER_USER
@@ -3635,9 +3648,10 @@ partitioned into non-empty pairwise-disjoint subsets. These subsets are called
clusters. Clusters with a cardinality of one are partitions. Each cluster is
owned by exactly one scheduler instance.
-A clustered scheduler configuration is optional. By default, all processors are
-managed by the :ref:`EDF SMP Scheduler <SchedulerSMPEDF>`. In order to use
-clustered scheduling the application designer has to answer two questions.
+A clustered scheduler configuration is optional. By default, up to 32
+processors are managed by the :ref:`EDF SMP Scheduler <SchedulerSMPEDF>`. In
+order to use clustered scheduling the application designer has to answer two
+questions.
#. How is the set of processors partitioned into clusters?
@@ -3651,13 +3665,13 @@ Configuration Step 1 - Scheduler Algorithms
Firstly, the application must select which scheduling algorithms are available
with the following defines
-- ``CONFIGURE_SCHEDULER_EDF_SMP``,
+- :ref:`CONFIGURE_SCHEDULER_EDF_SMP <CONFIGURE_SCHEDULER_EDF_SMP>`,
-- ``CONFIGURE_SCHEDULER_PRIORITY_AFFINITY_SMP``,
+- :ref:`CONFIGURE_SCHEDULER_PRIORITY_AFFINITY_SMP <CONFIGURE_SCHEDULER_PRIORITY_AFFINITY_SMP>`,
-- ``CONFIGURE_SCHEDULER_PRIORITY_SMP``, and
+- :ref:`CONFIGURE_SCHEDULER_PRIORITY_SMP <CONFIGURE_SCHEDULER_PRIORITY_SMP>`, and
-- ``CONFIGURE_SCHEDULER_SIMPLE_SMP``.
+- :ref:`CONFIGURE_SCHEDULER_SIMPLE_SMP <CONFIGURE_SCHEDULER_SIMPLE_SMP>`.
This is necessary to calculate the per-thread overhead introduced by the
schedulers. After these definitions the configuration file must ``#include
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