mirror of
https://git.rtems.org/rtems-docs/
synced 2025-05-15 05:57:08 +08:00
Sebastian Huber
parent
275f4a049c
commit
020d2e7e85
@ -23,222 +23,7 @@ Configuring a System
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bsp-related
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idle-task
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scheduler-general
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.. _ConfigurationSchedulersClustered:
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Clustered Scheduler Configuration
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=================================
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A clustered scheduler configuration is optional. It is an advanced
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configuration area and only necessary in specific circumstances.
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Clustered scheduling helps to control the worst-case latencies in a
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multiprocessor system (SMP). The goal is to reduce the amount of shared state
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in the system and thus prevention of lock contention. Modern multiprocessor
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systems tend to have several layers of data and instruction caches. With
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clustered scheduling it is possible to honour the cache topology of a system
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and thus avoid expensive cache synchronization traffic.
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We have clustered scheduling in case the set of processors of a system is
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partitioned into non-empty pairwise-disjoint subsets. These subsets are called
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clusters. Clusters with a cardinality of one are partitions. Each cluster is
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owned by exactly one scheduler.
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In order to use clustered scheduling the application designer has to answer two
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questions.
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#. How is the set of processors partitioned into clusters?
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#. Which scheduler algorithm is used for which cluster?
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The schedulers are statically configured.
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Configuration Step 1 - Scheduler Algorithms
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-------------------------------------------
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Firstly, the application must select which scheduling algorithms are available
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with the following defines
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- :ref:`CONFIGURE_SCHEDULER_EDF_SMP <CONFIGURE_SCHEDULER_EDF_SMP>`,
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- :ref:`CONFIGURE_SCHEDULER_PRIORITY_AFFINITY_SMP <CONFIGURE_SCHEDULER_PRIORITY_AFFINITY_SMP>`,
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- :ref:`CONFIGURE_SCHEDULER_PRIORITY_SMP <CONFIGURE_SCHEDULER_PRIORITY_SMP>`, and
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- :ref:`CONFIGURE_SCHEDULER_SIMPLE_SMP <CONFIGURE_SCHEDULER_SIMPLE_SMP>`.
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This is necessary to calculate the per-thread overhead introduced by the
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scheduler algorithms. After these definitions the configuration file must
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``#include <rtems/scheduler.h>`` to have access to scheduler-specific
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configuration macros.
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It is possible to make more than one scheduler algorithm available to the
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application. For example a :ref:`Simple Priority SMP Scheduler
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<SchedulerSMPPrioritySimple>` could be used in a partition for low latency
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tasks in addition to an :ref:`EDF SMP Scheduler <SchedulerSMPEDF>` for a
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general-purpose cluster. Since the per-thread overhead depends on the
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scheduler algorithm only the scheduler algorithms used by the application
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should be configured.
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Configuration Step 2 - Schedulers
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---------------------------------
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Each scheduler needs some data structures. Use the following macros to create
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the scheduler data structures for a particular scheduler identified in the
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configuration by ``name``.
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- ``RTEMS_SCHEDULER_EDF_SMP(name, max_cpu_count)``,
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- ``RTEMS_SCHEDULER_PRIORITY_AFFINITY_SMP(name, prio_count)``,
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- ``RTEMS_SCHEDULER_PRIORITY_SMP(name, prio_count)``, and
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- ``RTEMS_SCHEDULER_SIMPLE_SMP(name)``.
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The ``name`` parameter is used as part of a designator for scheduler-specific
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data structures, so the usual C/C++ designator rules apply. This ``name`` is
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not the scheduler object name. Additional parameters are scheduler-specific.
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.. _ConfigurationSchedulerTable:
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Configuration Step 3 - Scheduler Table
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--------------------------------------
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The schedulers are registered in the system via the scheduler table. To
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populate the scheduler table define ``CONFIGURE_SCHEDULER_TABLE_ENTRIES`` to a
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list of the following scheduler table entry initializers
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- ``RTEMS_SCHEDULER_TABLE_EDF_SMP(name, obj_name)``,
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- ``RTEMS_SCHEDULER_TABLE_PRIORITY_AFFINITY_SMP(name, obj_name)``,
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- ``RTEMS_SCHEDULER_TABLE_PRIORITY_SMP(name, obj_name)``, and
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- ``RTEMS_SCHEDULER_TABLE_SIMPLE_SMP(name, obj_name)``.
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The ``name`` parameter must correspond to the parameter defining the scheduler
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data structures of configuration step 2. The ``obj_name`` determines the
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scheduler object name and can be used in :ref:`rtems_scheduler_ident()
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<rtems_scheduler_ident>` to get the scheduler object identifier. The scheduler
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index is defined by the index of the scheduler table. It is a configuration
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error to add a scheduler multiple times to the scheduler table.
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Configuration Step 4 - Processor to Scheduler Assignment
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--------------------------------------------------------
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The last step is to define which processor uses which scheduler. For this
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purpose a scheduler assignment table must be defined. The entry count of this
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table must be equal to the configured maximum processors
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(:ref:`CONFIGURE_MAXIMUM_PROCESSORS <CONFIGURE_MAXIMUM_PROCESSORS>`). A
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processor assignment to a scheduler can be optional or mandatory. The boot
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processor must have a scheduler assigned. In case the system needs more
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mandatory processors than available then a fatal run-time error will occur. To
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specify the scheduler assignments define
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``CONFIGURE_SCHEDULER_ASSIGNMENTS`` to a list of
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- ``RTEMS_SCHEDULER_ASSIGN(scheduler_index, attr)`` and
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- ``RTEMS_SCHEDULER_ASSIGN_NO_SCHEDULER``
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macros. The ``scheduler_index`` parameter must be a valid index into the
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scheduler table defined by configuration step 3. The ``attr`` parameter
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defines the scheduler assignment attributes. By default, a scheduler
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assignment to a processor is optional. For the scheduler assignment attribute
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use one of the mutually exclusive variants
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- ``RTEMS_SCHEDULER_ASSIGN_DEFAULT``,
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- ``RTEMS_SCHEDULER_ASSIGN_PROCESSOR_MANDATORY``, and
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- ``RTEMS_SCHEDULER_ASSIGN_PROCESSOR_OPTIONAL``.
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It is possible to add/remove processors to/from schedulers at run-time, see
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:ref:`rtems_scheduler_add_processor() <rtems_scheduler_add_processor>` and
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:ref:`rtems_scheduler_remove_processor() <rtems_scheduler_remove_processor>`.
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Configuration Example
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---------------------
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The following example shows a scheduler configuration for a hypothetical
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product using two chip variants. One variant has four processors which is used
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for the normal product line and another provides eight processors for the
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high-performance product line. The first processor performs hard-real time
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control of actuators and sensors. The second processor is not used by RTEMS at
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all and runs a Linux instance to provide a graphical user interface. The
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additional processors are used for a worker thread pool to perform data
|
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processing operations.
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The processors managed by RTEMS use two Deterministic Priority SMP schedulers
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capable of dealing with 256 priority levels. The scheduler with index zero has
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the name ``"IO "``. The scheduler with index one has the name ``"WORK"``. The
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scheduler assignments of the first, third and fourth processor are mandatory,
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so the system must have at least four processors, otherwise a fatal run-time
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error will occur during system startup. The processor assignments for the
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fifth up to the eighth processor are optional so that the same application can
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be used for the normal and high-performance product lines. The second
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processor has no scheduler assigned and runs Linux. A hypervisor will ensure
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that the two systems cannot interfere in an undesirable way.
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.. code-block:: c
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#define CONFIGURE_MAXIMUM_PROCESSORS 8
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#define CONFIGURE_MAXIMUM_PRIORITY 255
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/* Configuration Step 1 - Scheduler Algorithms */
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#define CONFIGURE_SCHEDULER_PRIORITY_SMP
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#include <rtems/scheduler.h>
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/* Configuration Step 2 - Schedulers */
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RTEMS_SCHEDULER_PRIORITY_SMP(io, CONFIGURE_MAXIMUM_PRIORITY + 1);
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RTEMS_SCHEDULER_PRIORITY_SMP(work, CONFIGURE_MAXIMUM_PRIORITY + 1);
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/* Configuration Step 3 - Scheduler Table */
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#define CONFIGURE_SCHEDULER_TABLE_ENTRIES \
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RTEMS_SCHEDULER_TABLE_PRIORITY_SMP( \
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io, \
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rtems_build_name('I', 'O', ' ', ' ') \
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), \
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RTEMS_SCHEDULER_TABLE_PRIORITY_SMP( \
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work, \
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rtems_build_name('W', 'O', 'R', 'K') \
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)
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/* Configuration Step 4 - Processor to Scheduler Assignment */
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#define CONFIGURE_SCHEDULER_ASSIGNMENTS \
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RTEMS_SCHEDULER_ASSIGN(0, RTEMS_SCHEDULER_ASSIGN_PROCESSOR_MANDATORY), \
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RTEMS_SCHEDULER_ASSIGN_NO_SCHEDULER, \
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RTEMS_SCHEDULER_ASSIGN(1, RTEMS_SCHEDULER_ASSIGN_PROCESSOR_MANDATORY), \
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RTEMS_SCHEDULER_ASSIGN(1, RTEMS_SCHEDULER_ASSIGN_PROCESSOR_MANDATORY), \
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RTEMS_SCHEDULER_ASSIGN(1, RTEMS_SCHEDULER_ASSIGN_PROCESSOR_OPTIONAL), \
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RTEMS_SCHEDULER_ASSIGN(1, RTEMS_SCHEDULER_ASSIGN_PROCESSOR_OPTIONAL), \
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RTEMS_SCHEDULER_ASSIGN(1, RTEMS_SCHEDULER_ASSIGN_PROCESSOR_OPTIONAL), \
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RTEMS_SCHEDULER_ASSIGN(1, RTEMS_SCHEDULER_ASSIGN_PROCESSOR_OPTIONAL)
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Configuration Errors
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--------------------
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In case one of the scheduler indices in ``CONFIGURE_SCHEDULER_ASSIGNMENTS``
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is invalid a link-time error will occur with an undefined reference to
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``RTEMS_SCHEDULER_INVALID_INDEX``.
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Some fatal errors may occur in case of scheduler configuration inconsistencies
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or a lack of processors on the system. The fatal source is
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``RTEMS_FATAL_SOURCE_SMP``.
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- ``SMP_FATAL_BOOT_PROCESSOR_NOT_ASSIGNED_TO_SCHEDULER`` - the boot processor
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must have a scheduler assigned.
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- ``SMP_FATAL_MANDATORY_PROCESSOR_NOT_PRESENT`` - there exists a mandatory
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processor beyond the range of physically or virtually available processors.
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The processor demand must be reduced for this system.
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- ``SMP_FATAL_START_OF_MANDATORY_PROCESSOR_FAILED`` - the start of a mandatory
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processor failed during system initialization. The system may not have this
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processor at all or it could be a problem with a boot loader for example.
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Check the ``CONFIGURE_SCHEDULER_ASSIGNMENTS`` definition.
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- ``SMP_FATAL_MULTITASKING_START_ON_UNASSIGNED_PROCESSOR`` - it is not allowed
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to start multitasking on a processor with no scheduler assigned.
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scheduler-clustered
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Device Driver Configuration
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===========================
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219
c-user/config/scheduler-clustered.rst
Normal file
219
c-user/config/scheduler-clustered.rst
Normal file
@ -0,0 +1,219 @@
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.. SPDX-License-Identifier: CC-BY-SA-4.0
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.. Copyright (C) 1988, 2008 On-Line Applications Research Corporation (OAR)
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.. _ConfigurationSchedulersClustered:
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Clustered Scheduler Configuration
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=================================
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A clustered scheduler configuration is optional. It is an advanced
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configuration area and only necessary in specific circumstances.
|
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Clustered scheduling helps to control the worst-case latencies in a
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multiprocessor system (SMP). The goal is to reduce the amount of shared state
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in the system and thus prevention of lock contention. Modern multiprocessor
|
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systems tend to have several layers of data and instruction caches. With
|
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clustered scheduling it is possible to honour the cache topology of a system
|
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and thus avoid expensive cache synchronization traffic.
|
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We have clustered scheduling in case the set of processors of a system is
|
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partitioned into non-empty pairwise-disjoint subsets. These subsets are called
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clusters. Clusters with a cardinality of one are partitions. Each cluster is
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owned by exactly one scheduler.
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|
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In order to use clustered scheduling the application designer has to answer two
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questions.
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#. How is the set of processors partitioned into clusters?
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#. Which scheduler algorithm is used for which cluster?
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The schedulers are statically configured.
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Configuration Step 1 - Scheduler Algorithms
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-------------------------------------------
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Firstly, the application must select which scheduling algorithms are available
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with the following defines
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- :ref:`CONFIGURE_SCHEDULER_EDF_SMP <CONFIGURE_SCHEDULER_EDF_SMP>`,
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- :ref:`CONFIGURE_SCHEDULER_PRIORITY_AFFINITY_SMP <CONFIGURE_SCHEDULER_PRIORITY_AFFINITY_SMP>`,
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- :ref:`CONFIGURE_SCHEDULER_PRIORITY_SMP <CONFIGURE_SCHEDULER_PRIORITY_SMP>`, and
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- :ref:`CONFIGURE_SCHEDULER_SIMPLE_SMP <CONFIGURE_SCHEDULER_SIMPLE_SMP>`.
|
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This is necessary to calculate the per-thread overhead introduced by the
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scheduler algorithms. After these definitions the configuration file must
|
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``#include <rtems/scheduler.h>`` to have access to scheduler-specific
|
||||
configuration macros.
|
||||
|
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It is possible to make more than one scheduler algorithm available to the
|
||||
application. For example a :ref:`Simple Priority SMP Scheduler
|
||||
<SchedulerSMPPrioritySimple>` could be used in a partition for low latency
|
||||
tasks in addition to an :ref:`EDF SMP Scheduler <SchedulerSMPEDF>` for a
|
||||
general-purpose cluster. Since the per-thread overhead depends on the
|
||||
scheduler algorithm only the scheduler algorithms used by the application
|
||||
should be configured.
|
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|
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Configuration Step 2 - Schedulers
|
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---------------------------------
|
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|
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Each scheduler needs some data structures. Use the following macros to create
|
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the scheduler data structures for a particular scheduler identified in the
|
||||
configuration by ``name``.
|
||||
|
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- ``RTEMS_SCHEDULER_EDF_SMP(name, max_cpu_count)``,
|
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- ``RTEMS_SCHEDULER_PRIORITY_AFFINITY_SMP(name, prio_count)``,
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- ``RTEMS_SCHEDULER_PRIORITY_SMP(name, prio_count)``, and
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- ``RTEMS_SCHEDULER_SIMPLE_SMP(name)``.
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The ``name`` parameter is used as part of a designator for scheduler-specific
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data structures, so the usual C/C++ designator rules apply. This ``name`` is
|
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not the scheduler object name. Additional parameters are scheduler-specific.
|
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.. _ConfigurationSchedulerTable:
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Configuration Step 3 - Scheduler Table
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--------------------------------------
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The schedulers are registered in the system via the scheduler table. To
|
||||
populate the scheduler table define ``CONFIGURE_SCHEDULER_TABLE_ENTRIES`` to a
|
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list of the following scheduler table entry initializers
|
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|
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- ``RTEMS_SCHEDULER_TABLE_EDF_SMP(name, obj_name)``,
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- ``RTEMS_SCHEDULER_TABLE_PRIORITY_AFFINITY_SMP(name, obj_name)``,
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- ``RTEMS_SCHEDULER_TABLE_PRIORITY_SMP(name, obj_name)``, and
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- ``RTEMS_SCHEDULER_TABLE_SIMPLE_SMP(name, obj_name)``.
|
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|
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The ``name`` parameter must correspond to the parameter defining the scheduler
|
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data structures of configuration step 2. The ``obj_name`` determines the
|
||||
scheduler object name and can be used in :ref:`rtems_scheduler_ident()
|
||||
<rtems_scheduler_ident>` to get the scheduler object identifier. The scheduler
|
||||
index is defined by the index of the scheduler table. It is a configuration
|
||||
error to add a scheduler multiple times to the scheduler table.
|
||||
|
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Configuration Step 4 - Processor to Scheduler Assignment
|
||||
--------------------------------------------------------
|
||||
|
||||
The last step is to define which processor uses which scheduler. For this
|
||||
purpose a scheduler assignment table must be defined. The entry count of this
|
||||
table must be equal to the configured maximum processors
|
||||
(:ref:`CONFIGURE_MAXIMUM_PROCESSORS <CONFIGURE_MAXIMUM_PROCESSORS>`). A
|
||||
processor assignment to a scheduler can be optional or mandatory. The boot
|
||||
processor must have a scheduler assigned. In case the system needs more
|
||||
mandatory processors than available then a fatal run-time error will occur. To
|
||||
specify the scheduler assignments define
|
||||
``CONFIGURE_SCHEDULER_ASSIGNMENTS`` to a list of
|
||||
|
||||
- ``RTEMS_SCHEDULER_ASSIGN(scheduler_index, attr)`` and
|
||||
|
||||
- ``RTEMS_SCHEDULER_ASSIGN_NO_SCHEDULER``
|
||||
|
||||
macros. The ``scheduler_index`` parameter must be a valid index into the
|
||||
scheduler table defined by configuration step 3. The ``attr`` parameter
|
||||
defines the scheduler assignment attributes. By default, a scheduler
|
||||
assignment to a processor is optional. For the scheduler assignment attribute
|
||||
use one of the mutually exclusive variants
|
||||
|
||||
- ``RTEMS_SCHEDULER_ASSIGN_DEFAULT``,
|
||||
|
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- ``RTEMS_SCHEDULER_ASSIGN_PROCESSOR_MANDATORY``, and
|
||||
|
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- ``RTEMS_SCHEDULER_ASSIGN_PROCESSOR_OPTIONAL``.
|
||||
|
||||
It is possible to add/remove processors to/from schedulers at run-time, see
|
||||
:ref:`rtems_scheduler_add_processor() <rtems_scheduler_add_processor>` and
|
||||
:ref:`rtems_scheduler_remove_processor() <rtems_scheduler_remove_processor>`.
|
||||
|
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Configuration Example
|
||||
---------------------
|
||||
|
||||
The following example shows a scheduler configuration for a hypothetical
|
||||
product using two chip variants. One variant has four processors which is used
|
||||
for the normal product line and another provides eight processors for the
|
||||
high-performance product line. The first processor performs hard-real time
|
||||
control of actuators and sensors. The second processor is not used by RTEMS at
|
||||
all and runs a Linux instance to provide a graphical user interface. The
|
||||
additional processors are used for a worker thread pool to perform data
|
||||
processing operations.
|
||||
|
||||
The processors managed by RTEMS use two Deterministic Priority SMP schedulers
|
||||
capable of dealing with 256 priority levels. The scheduler with index zero has
|
||||
the name ``"IO "``. The scheduler with index one has the name ``"WORK"``. The
|
||||
scheduler assignments of the first, third and fourth processor are mandatory,
|
||||
so the system must have at least four processors, otherwise a fatal run-time
|
||||
error will occur during system startup. The processor assignments for the
|
||||
fifth up to the eighth processor are optional so that the same application can
|
||||
be used for the normal and high-performance product lines. The second
|
||||
processor has no scheduler assigned and runs Linux. A hypervisor will ensure
|
||||
that the two systems cannot interfere in an undesirable way.
|
||||
|
||||
.. code-block:: c
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||||
|
||||
#define CONFIGURE_MAXIMUM_PROCESSORS 8
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#define CONFIGURE_MAXIMUM_PRIORITY 255
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/* Configuration Step 1 - Scheduler Algorithms */
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#define CONFIGURE_SCHEDULER_PRIORITY_SMP
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#include <rtems/scheduler.h>
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/* Configuration Step 2 - Schedulers */
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RTEMS_SCHEDULER_PRIORITY_SMP(io, CONFIGURE_MAXIMUM_PRIORITY + 1);
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RTEMS_SCHEDULER_PRIORITY_SMP(work, CONFIGURE_MAXIMUM_PRIORITY + 1);
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/* Configuration Step 3 - Scheduler Table */
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#define CONFIGURE_SCHEDULER_TABLE_ENTRIES \
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RTEMS_SCHEDULER_TABLE_PRIORITY_SMP( \
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io, \
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rtems_build_name('I', 'O', ' ', ' ') \
|
||||
), \
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RTEMS_SCHEDULER_TABLE_PRIORITY_SMP( \
|
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work, \
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rtems_build_name('W', 'O', 'R', 'K') \
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||||
)
|
||||
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||||
/* Configuration Step 4 - Processor to Scheduler Assignment */
|
||||
#define CONFIGURE_SCHEDULER_ASSIGNMENTS \
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RTEMS_SCHEDULER_ASSIGN(0, RTEMS_SCHEDULER_ASSIGN_PROCESSOR_MANDATORY), \
|
||||
RTEMS_SCHEDULER_ASSIGN_NO_SCHEDULER, \
|
||||
RTEMS_SCHEDULER_ASSIGN(1, RTEMS_SCHEDULER_ASSIGN_PROCESSOR_MANDATORY), \
|
||||
RTEMS_SCHEDULER_ASSIGN(1, RTEMS_SCHEDULER_ASSIGN_PROCESSOR_MANDATORY), \
|
||||
RTEMS_SCHEDULER_ASSIGN(1, RTEMS_SCHEDULER_ASSIGN_PROCESSOR_OPTIONAL), \
|
||||
RTEMS_SCHEDULER_ASSIGN(1, RTEMS_SCHEDULER_ASSIGN_PROCESSOR_OPTIONAL), \
|
||||
RTEMS_SCHEDULER_ASSIGN(1, RTEMS_SCHEDULER_ASSIGN_PROCESSOR_OPTIONAL), \
|
||||
RTEMS_SCHEDULER_ASSIGN(1, RTEMS_SCHEDULER_ASSIGN_PROCESSOR_OPTIONAL)
|
||||
|
||||
Configuration Errors
|
||||
--------------------
|
||||
|
||||
In case one of the scheduler indices in ``CONFIGURE_SCHEDULER_ASSIGNMENTS``
|
||||
is invalid a link-time error will occur with an undefined reference to
|
||||
``RTEMS_SCHEDULER_INVALID_INDEX``.
|
||||
|
||||
Some fatal errors may occur in case of scheduler configuration inconsistencies
|
||||
or a lack of processors on the system. The fatal source is
|
||||
``RTEMS_FATAL_SOURCE_SMP``.
|
||||
|
||||
- ``SMP_FATAL_BOOT_PROCESSOR_NOT_ASSIGNED_TO_SCHEDULER`` - the boot processor
|
||||
must have a scheduler assigned.
|
||||
|
||||
- ``SMP_FATAL_MANDATORY_PROCESSOR_NOT_PRESENT`` - there exists a mandatory
|
||||
processor beyond the range of physically or virtually available processors.
|
||||
The processor demand must be reduced for this system.
|
||||
|
||||
- ``SMP_FATAL_START_OF_MANDATORY_PROCESSOR_FAILED`` - the start of a mandatory
|
||||
processor failed during system initialization. The system may not have this
|
||||
processor at all or it could be a problem with a boot loader for example.
|
||||
Check the ``CONFIGURE_SCHEDULER_ASSIGNMENTS`` definition.
|
||||
|
||||
- ``SMP_FATAL_MULTITASKING_START_ON_UNASSIGNED_PROCESSOR`` - it is not allowed
|
||||
to start multitasking on a processor with no scheduler assigned.
|
||||
Loading…
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Reference in New Issue
Block a user