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c-user: Rework clustered scheduling configuration
This commit is contained in:
Sebastian Huber
parent
464d541653
commit
c65aeed3cd
@ -3624,8 +3624,8 @@ Clustered Scheduler Configuration
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=================================
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Clustered scheduling helps to control the worst-case latencies in a
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multi-processor system. The goal is to reduce the amount of shared state in
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the system and thus prevention of lock contention. Modern multi-processor
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multi-processor 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 multi-processor
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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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@ -3633,161 +3633,195 @@ 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 instance. In order to use clustered scheduling
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the application designer has to answer two questions.
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owned by exactly one scheduler instance.
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A clustered scheduler configuration is optional. By default, all processors are
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managed by the :ref:`EDF SMP Scheduler <SchedulerSMPEDF>`. In order to use
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clustered scheduling the application designer has to answer two questions.
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#. How is the set of processors partitioned into clusters?
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#. Which scheduler is used for which cluster?
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#. Which scheduler algorithm is used for which cluster?
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CONFIGURATION:
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The schedulers in an SMP system are statically configured on RTEMS.
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Firstly the application must select which scheduling algorithms are
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available with the following defines
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The schedulers are statically configured.
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- ``CONFIGURE_SCHEDULER_PRIORITY_SMP``,
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Configuration Step 1 - Scheduler Algorithms
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-------------------------------------------
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- ``CONFIGURE_SCHEDULER_SIMPLE_SMP``, and
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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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- ``CONFIGURE_SCHEDULER_PRIORITY_AFFINITY_SMP``.
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- ``CONFIGURE_SCHEDULER_EDF_SMP``,
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This is necessary to calculate the per-thread overhead introduced by the
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schedulers. After these definitions the configuration file must ``#include
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<rtems/scheduler.h>`` to have access to scheduler specific configuration
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macros. Each scheduler needs a context to store state information at
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run-time. To provide a context for each scheduler is the next step. Use
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the following macros to create scheduler contexts
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- ``CONFIGURE_SCHEDULER_PRIORITY_AFFINITY_SMP``,
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- ``RTEMS_SCHEDULER_CONTEXT_PRIORITY_SMP(name, prio_count)``,
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- ``CONFIGURE_SCHEDULER_PRIORITY_SMP``, and
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- ``RTEMS_SCHEDULER_CONTEXT_SIMPLE_SMP(name)``, and
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- ``CONFIGURE_SCHEDULER_SIMPLE_SMP``.
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- ``RTEMS_SCHEDULER_CONTEXT_PRIORITY_AFFINITY_SMP(name, prio_count)``.
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This is necessary to calculate the per-thread overhead introduced by the
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schedulers. After these definitions the configuration file must ``#include
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<rtems/scheduler.h>`` to have access to scheduler-specific configuration
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macros.
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The ``name`` parameter is used as part of a designator for a global
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variable, so the usual C/C++ designator rules apply. Additional parameters
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are scheduler specific. The schedulers are registered in the system via
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the scheduler table. To create the scheduler table define
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``CONFIGURE_SCHEDULER_CONTROLS`` to a list of the following scheduler
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control initializers
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Configuration Step 2 - Schedulers
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---------------------------------
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- ``RTEMS_SCHEDULER_CONTROL_PRIORITY_SMP(name, obj_name)``,
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Each scheduler needs a context to store state information at run-time. Use the
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following macros to create scheduler contexts
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- ``RTEMS_SCHEDULER_CONTROL_SIMPLE_SMP(name, obj_name)``, and
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- ``RTEMS_SCHEDULER_CONTEXT_EDF_SMP(name, max_cpu_count)``,
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- ``RTEMS_SCHEDULER_CONTROL_PRIORITY_AFFINITY_SMP(name, obj_name)``.
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- ``RTEMS_SCHEDULER_CONTEXT_PRIORITY_AFFINITY_SMP(name, prio_count)``,
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The ``name`` parameter must correspond to the parameter defining the
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scheduler context. The ``obj_name`` determines the scheduler object name
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and can be used in ``rtems_scheduler_ident()`` to get the scheduler object
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identifier.
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- ``RTEMS_SCHEDULER_CONTEXT_PRIORITY_SMP(name, prio_count)``, and
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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
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this table must be equal to the configured maximum processors
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(``CONFIGURE_MAXIMUM_PROCESSORS``). A processor assignment to a
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scheduler can be optional or mandatory. The boot processor must have a
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scheduler assigned. In case the system needs more mandatory processors
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than available then a fatal run-time error will occur. To specify the
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scheduler assignments define ``CONFIGURE_SMP_SCHEDULER_ASSIGNMENTS`` to a
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list of ``RTEMS_SCHEDULER_ASSIGN(index, attr)`` and
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``RTEMS_SCHEDULER_ASSIGN_NO_SCHEDULER`` macros. The ``index`` parameter
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must be a valid index into the scheduler table. 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
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attribute use one of the mutually exclusive variants
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- ``RTEMS_SCHEDULER_CONTEXT_SIMPLE_SMP(name)``.
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- ``RTEMS_SCHEDULER_ASSIGN_DEFAULT``,
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The ``name`` parameter is used as part of a designator for a global variable,
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so the usual C/C++ designator rules apply. This ``name`` is not the scheduler
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object name. Additional parameters are scheduler-specific.
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- ``RTEMS_SCHEDULER_ASSIGN_PROCESSOR_MANDATORY``, and
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.. _ConfigurationSchedulerTable:
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- ``RTEMS_SCHEDULER_ASSIGN_PROCESSOR_OPTIONAL``.
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Configuration Step 3 - Scheduler Table
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--------------------------------------
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It is possible to add/remove processors to/from scheduler instances at
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run-time, see :ref:`rtems_scheduler_add_processor` and
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:ref:`rtems_scheduler_remove_processor`.
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The schedulers are registered in the system via the scheduler table.
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To create the scheduler table define ``CONFIGURE_SCHEDULER_CONTROLS`` to a list
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of the following scheduler control initializers
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ERRORS:
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In case one of the scheduler indices
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in``CONFIGURE_SMP_SCHEDULER_ASSIGNMENTS`` is invalid a link-time error will
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occur with an undefined reference to ``RTEMS_SCHEDULER_INVALID_INDEX``.
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- ``RTEMS_SCHEDULER_CONTROL_EDF_SMP(name, obj_name)``,
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Some fatal errors may occur in case of scheduler configuration
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inconsistencies or a lack of processors on the system. The fatal source is
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``RTEMS_FATAL_SOURCE_SMP``. None of the errors is internal.
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- ``RTEMS_SCHEDULER_CONTROL_PRIORITY_AFFINITY_SMP(name, obj_name)``,
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- ``SMP_FATAL_BOOT_PROCESSOR_NOT_ASSIGNED_TO_SCHEDULER`` - the boot
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processor must have a scheduler assigned.
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- ``RTEMS_SCHEDULER_CONTROL_PRIORITY_SMP(name, obj_name)``, and
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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
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processors. The processor demand must be reduced for this system.
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- ``RTEMS_SCHEDULER_CONTROL_SIMPLE_SMP(name, obj_name)``.
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- ``SMP_FATAL_START_OF_MANDATORY_PROCESSOR_FAILED`` - the start of a
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mandatory processor failed during system initialization. The system may
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not have this processor at all or it could be a problem with a boot
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loader for example. Check the ``CONFIGURE_SMP_SCHEDULER_ASSIGNMENTS``
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definition.
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The ``name`` parameter must correspond to the parameter defining the scheduler
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context. The ``obj_name`` determines the scheduler object name and can be used
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in :ref:`rtems_scheduler_ident() <rtems_scheduler_ident>` to get the scheduler
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object identifier. The scheduler index is defined by the index of the
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scheduler table. It is a configuration error to add a scheduler multiple times
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to the scheduler table.
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- ``SMP_FATAL_MULTITASKING_START_ON_UNASSIGNED_PROCESSOR`` - it is not
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allowed to start multitasking on a processor with no scheduler assigned.
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Configuration Step 4 - Processor to Scheduler Assignment
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--------------------------------------------------------
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EXAMPLE:
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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
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used for the normal product line and another provides eight processors for
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the high-performance product line. The first processor performs hard-real
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time control of actuators and sensors. The second processor is not used by
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RTEMS at all and runs a Linux instance to provide a graphical user
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interface. The additional processors are used for a worker thread pool to
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perform data processing operations.
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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_SMP_SCHEDULER_ASSIGNMENTS`` to a list of
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The processors managed by RTEMS use two Deterministic Priority scheduler
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instances capable of dealing with 256 priority levels. The scheduler with
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index zero has the name ``"IO "``. The scheduler with index one has the
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name ``"WORK"``. The scheduler assignments of the first, third and fourth
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processor are mandatory, so the system must have at least four processors,
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otherwise a fatal run-time error will occur during system startup. The
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processor assignments for the fifth up to the eighth processor are optional
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so that the same application can be used for the normal and
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high-performance product lines. The second processor has no scheduler
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assigned and runs Linux. A hypervisor will ensure that the two systems
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cannot interfere in an undesirable way.
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- ``RTEMS_SCHEDULER_ASSIGN(scheduler_index, attr)`` and
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.. code-block:: c
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- ``RTEMS_SCHEDULER_ASSIGN_NO_SCHEDULER``
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#define CONFIGURE_MAXIMUM_PROCESSORS 8
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#define CONFIGURE_MAXIMUM_PRIORITY 255
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macros. The ``scheduler_index`` parameter must
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be a valid index into the scheduler table. The ``attr`` parameter defines the
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scheduler assignment attributes. By default, a scheduler assignment to a
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processor is optional. For the scheduler assignment attribute use one of the
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mutually exclusive variants
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/* Make the scheduler algorithm available */
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#define CONFIGURE_SCHEDULER_PRIORITY_SMP
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#include <rtems/scheduler.h>
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- ``RTEMS_SCHEDULER_ASSIGN_DEFAULT``,
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/* Create contexts for the two scheduler instances */
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RTEMS_SCHEDULER_CONTEXT_PRIORITY_SMP(io, CONFIGURE_MAXIMUM_PRIORITY + 1);
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RTEMS_SCHEDULER_CONTEXT_PRIORITY_SMP(work, CONFIGURE_MAXIMUM_PRIORITY + 1);
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- ``RTEMS_SCHEDULER_ASSIGN_PROCESSOR_MANDATORY``, and
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/* Define the scheduler table */
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#define CONFIGURE_SCHEDULER_CONTROLS \\
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RTEMS_SCHEDULER_CONTROL_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_CONTROL_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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- ``RTEMS_SCHEDULER_ASSIGN_PROCESSOR_OPTIONAL``.
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/* Define the initial processor to scheduler assignments */
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#define CONFIGURE_SMP_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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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_CONTEXT_PRIORITY_SMP(io, CONFIGURE_MAXIMUM_PRIORITY + 1);
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RTEMS_SCHEDULER_CONTEXT_PRIORITY_SMP(work, CONFIGURE_MAXIMUM_PRIORITY + 1);
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/* Configuration Step 3 - Scheduler Table */
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#define CONFIGURE_SCHEDULER_CONTROLS \\
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RTEMS_SCHEDULER_CONTROL_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_CONTROL_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_SMP_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_SMP_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_SMP_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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Device Driver Table
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===================
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@ -564,8 +564,8 @@ DIRECTIVE STATUS CODES:
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DESCRIPTION:
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Identifies a scheduler by its name. The scheduler name is determined by
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the scheduler configuration. See :ref:`ConfigurationSchedulersClustered`
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and :ref:`Configuring a Scheduler Name`.
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the scheduler configuration. See :ref:`ConfigurationSchedulerTable`
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and :ref:`CONFIGURE_SCHEDULER_NAME`.
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NOTES:
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None.
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