1. Cheddar – Real Time Simulator Scheduling with task dependencies

2. Task Dependencies Meaning…… resources shared by several tasks (ex : semaphores) precedencies relationship between several tasks (like constraints between the end of a task and the start of another one).

3. Types Of Tools Shared resources analysis tools Task precedencies analysis tools Buffer analysis tools

4. Task precedencies analysis tools With Cheddar, dependencies are links between at least two tasks Three different types of dependencies  Precedencies  Message and  Buffer dependencies

5. Types Of Dependencies Precendencies express order constraints between end or begin of task execution. Message dependencies expressed relationship between a sender and a receiver task of a given message. Buffer dependencies expressed relationship between producer and consumer of data in a given buffer.

6. Precedencies Graph Tasks -> circles. Messages -> rectangles. Buffers -> envelopes.

7. Typical Precedencies Graph

8. An Example Different Parameters Periodic Tasks - T1(4,1), T2(5,2), T3(5,1) Aperiodic Task – T4(10,2) EDF Scheduler Preemptive Precedence: T3  T2

9. Precedence Graph

10. Simulation Result

11. Some Limitations… Capacity Is Integer Only. Aperiodic Job Cannot Be Done On Rate Monotonic Scheduler. For Task Precedencies, Tasks Must Have Equal Periods…

12. Project Files Information stored during a simulation can be saved into Project Files A project file is a XML file Correct structure of the Project Files can be checked by the tool dump_sys dump_sys just read, parses and displays to the screen the content of a XML Cheddar project file.