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

Scheduling Basic Concepts Ref: Hard Real-Time Computing Systems Giorgio Buttazzo Processes - Tasks - Threads. Nostalgia. Apollo Guidance Computer First Microprocessor Microcontroller. Automobile Computers: 2006: 1-2 million lines of code

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

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  1. SchedulingBasic ConceptsRef: Hard Real-Time Computing SystemsGiorgio ButtazzoProcesses - Tasks - Threads

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

  3. The Osborne I (1981) First Portable Computer Software: CPM Word Star SuperCalc Dbase II CBasic • Hardware: • Dual 5¼-inch floppy disk drives • 4 MHzZ80CPU • 65 kilobytes main memory • Fold-down keyboard doubling as the computer case's lid • 5-inch, 52 character × 24 line monochromeCRT display • Parallelprinter port • Serial port for use with external modems or serial printers

  4. 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)

  5. Ready Queue

  6. Definition of Schedule What does it say?

  7. Preemptive Schedules

  8. Categories of Schedules

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

  10. Real-Time Task Parameters

  11. Real-Time Task Parameters

  12. Periodic vs Aperiodic Tasks

  13. Precedence Constraints

  14. Precedence Example

  15. Critical Sections Binary Semaphore

  16. Critical Section Example

  17. Critical Section Model

  18. Definition of Scheduling Problems

  19. Classification of Scheduling Algorithms

  20. Guarantee-Based Algorithms

  21. Domino Effect Degradation

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