1. Scheduling Basic Concepts Ref: Hard Real-Time Computing Systems Giorgio Buttazzo Processes - Tasks - Threads

2. Nostalgia Automobile Computers: 2006: 1-2 million lines of code 2010: 10 million lines of code Apollo Guidance Computer First Microprocessor Microcontroller 99%+ of today’s computers are in embedded systems

3. The Osborne I (1981) Hardware: Dual 5¼-inch floppy disk drivesfloppy disk 4 MHz Z80 CPUMHzZ80CPU 65 kilobytes main memorykilobytesmemory Fold-down keyboard doubling as the computer case's lidkeyboard 5-inch, 52 character × 24 line monochrome CRT displaymonochromeCRT Parallel printer portParallelprinter Serial port for use with external modems or serial printersSerial portmodems Software: CPM Word Star SuperCalc Dbase II CBasic First Portable Computer

5. Orientation Schedule: An assignment of tasks to the processor, so that each task is executed until completion Scheduling Policy: Tasks assigned according to a predefined criterion Scheduling Algorithm: The set of rules that determines the ordering of tasks Active Task  Ready Task  Running Task (Ready Queue) (Dispatching)

6. Ready Queue

7. Definition of Schedule What does it say?

8. Preemptive Schedules

9. Categories of Schedules

10. Deadlines Deadline: Absolute – with respect to real-time (time zero) Relative – with respect to arrival time

11. Real-Time Task Parameters

13. Periodic vs Aperiodic Tasks

14. Precedence Constraints

15. Precedence Example

16. Critical Sections Binary Semaphore

17. Critical Section Example

18. Critical Section Model

19. Definition of Scheduling Problems

20. Classification of Scheduling Algorithms

21. Guarantee-Based Algorithms

22. Domino Effect Degradation