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Diffstat (limited to 'c-user/symmetric_multiprocessing_services.rst')
| -rw-r--r-- | c-user/symmetric_multiprocessing_services.rst | 61 |
1 files changed, 46 insertions, 15 deletions
diff --git a/c-user/symmetric_multiprocessing_services.rst b/c-user/symmetric_multiprocessing_services.rst index 0065f0c..80e3f8c 100644 --- a/c-user/symmetric_multiprocessing_services.rst +++ b/c-user/symmetric_multiprocessing_services.rst @@ -10,31 +10,27 @@ Symmetric Multiprocessing (SMP) Introduction ============ -The Symmetric Multiprocessing (SMP) support of the RTEMS 4.11.0 and later is available -on +The Symmetric Multiprocessing (SMP) support of the RTEMS 4.12 is available on -- ARM, +- ARMv7-A, - PowerPC, and - SPARC. -It must be explicitly enabled via the ``--enable-smp`` configure command line -option. To enable SMP in the application configuration see :ref:`Enable SMP -Support for Applications`. The default scheduler for SMP applications supports -up to 32 processors and is a global fixed priority scheduler, see also -:ref:`Configuring Clustered Schedulers`. For example applications -see:file:`testsuites/smptests`. - .. warning:: - The SMP support in the release of RTEMS is a work in progress. Before you - start using this RTEMS version for SMP ask on the RTEMS mailing list. + The SMP support must be explicitly enabled via the ``--enable-smp`` + configure command line option for the :term:`BSP` build. -This chapter describes the services related to Symmetric Multiprocessing -provided by RTEMS. +RTEMS is supposed to be a real-time operating system. What does this mean in +the context of SMP? The RTEMS interpretation of real-time on SMP is the +support for :ref:`ClusteredScheduling` with priority based schedulers and +adequate locking protocols. One aim is to enable a schedulability analysis +under the sporadic task model :cite:`Brandenburg:2011:SL` +:cite:`Burns:2013:MrsP`. -The application level services currently provided are: +The directives provided by the SMP support are: - rtems_get_processor_count_ - Get processor count @@ -43,6 +39,39 @@ The application level services currently provided are: Background ========== +Application Configuration +------------------------- + +By default, the maximum processor count is set to one in the application +configuration. To enable SMP, the application configuration option +:ref:`CONFIGURE_SMP_MAXIMUM_PROCESSORS <CONFIGURE_SMP_MAXIMUM_PROCESSORS>` must +be defined to a value greater than one. It is recommended to use the smallest +value suitable for the application in order to safe memory. Each processor +needs an idle thread and interrupt stack for example. + +The default scheduler for SMP applications supports up to 32 processors and is +a global fixed priority scheduler, see also :ref:`Configuring Clustered +Schedulers`. + +The following compile-time test can be used to check if the SMP support is +available or not. + +.. code-block:: c + + #include <rtems.h> + + #ifdef RTEMS_SMP + #warning "SMP support is enabled" + #else + #warning "SMP support is disabled" + #endif + +Examples +-------- + +For example applications see `testsuites/smptests +<https://git.rtems.org/rtems/tree/testsuites/smptests>`_. + Uniprocessor versus SMP Parallelism ----------------------------------- @@ -140,6 +169,8 @@ to another. There are four reasons why tasks migrate in RTEMS. Task migration should be avoided so that the working set of a task can stay on the most local cache level. +.. _ClusteredScheduling: + Clustered Scheduling -------------------- |