Книга: Real-Time Concepts for Embedded Systems

14.5 Points to Remember

14.5 Points to Remember

Some points to remember include the following:

· An outside-in approach can be used to decompose applications at the top level.

· Device dependencies can be used to decompose applications.

· Event dependencies can be used to decompose applications.

· Timing dependencies can be used to decompose applications.

· Levels of criticality of workload involved can be used to decompose applications.

· Functional cohesion, temporal cohesion, or sequential cohesion can be used either to form a task or to combine tasks.

· Rate Monotonic Scheduling can be summarized by stating that a task's priority depends on its period-the shorter the period, the higher the priority. RMS, when implemented appropriately, produces stable and predictable performance.

· Schedulability analysis only looks at how systems meet temporal requirements, not functional requirements.

· Six assumptions are associated with the basic RMA:

 ? all of the tasks are periodic,

 ? the tasks are independent of each other and that no interactions occur among tasks,

 ? a task's deadline is the beginning of its next period,

 ? each task has a constant execution time that does not vary over time,

 ? all of the tasks have the same level of criticality, and

 ? aperiodic tasks are limited to initialization and failure recovery work and that these aperiodic tasks do not have hard deadlines.

· Basic RMA does not account for task synchronization and aperiodic tasks.

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