--- doc/user/smp.t | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+)
diff --git a/doc/user/smp.t b/doc/user/smp.t index 1b4849a..ba700e0 100644 --- a/doc/user/smp.t +++ b/doc/user/smp.t @@ -147,6 +147,44 @@ another processor. So if we enable interrupts during this transition we have to provide an alternative task independent stack for this time frame. This issue needs further investigation. +@subsection Clustered/Partitioned Scheduling + +We have clustered scheduling in case the set of processors of a system is +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. + +Clustered/partitioned scheduling helps to control the worst-case latencies in +the system, see @cite{Brandenburg, Bj??rn B.: Scheduling and Locking in +Multiprocessor Real-Time Operating Systems. PhD thesis, 2011. +@uref{http://www.cs.unc.edu/~bbb/diss/brandenburg-diss.pdf}}. The goal is to +reduce the amount of shared state in the system and thus prevention of lock +contention. Modern multi-processor systems tend to have several layers of data +and instruction caches. With clustered/partitioned scheduling it is possible to +honour the cache topology of a system and thus avoid expensive cache +synchronization traffic. It is easy to implement. The problem is to provide +synchronization primitives for inter-partition synchronization. In RTEMS there +are currently three means available + +@itemize @bullet +@item events, +@item message queues, and +@item semaphores using the @ref{Semaphore Manager Multiprocessor Resource +Sharing Protocol} (MrsP). +@end itemize + +The clustered/partitioned scheduling approach enables separation of functions +with real-time requirements and functions that profit from fairness and high +throughput provided the scheduler instances are fully decoupled and adequate +intra-partition synchronization primitives are used. This is work in progress. + +For the configuration of clustered/partitioned schedulers see @ref{Configuring +a System Configuring Clustered/Partitioned Schedulers}. + +To set the scheduler of a task see @ref{Symmetric Multiprocessing Services +SCHEDULER_IDENT - Get ID of a scheduler} and @ref{Symmetric Multiprocessing +Services TASK_SET_SCHEDULER - Set scheduler of a task}. + @subsection Scheduler Helping Protocol The scheduler provides a helping protocol to support locking protocols like -- 1.8.4.5
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