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Scheduling Basic Concepts Processes - Tasks - Threads

Scheduling Basic Concepts Processes - Tasks - Threads. Nostalgia. Apollo Guidance Computer First Microprocessor Microcontroller. Automobile Computers: 2006: 1-2 million lines of code 2010: 10 million lines of code.

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Scheduling Basic Concepts Processes - Tasks - Threads

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  1. SchedulingBasic ConceptsProcesses - 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. Formal Definition of Schedule See text page 22 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. Precedence Graph for 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

  23. Best Effort Algorithms

  24. Metrics for Performance Evaluation

  25. Attempting to Minimize Lateness

  26. Example Cost Functions

  27. Scheduling Anomalies

  28. Example

  29. Adding a processor

  30. Reducing Computation Times

  31. Weaken Constraints

  32. Resource Constraints

  33. Exorcises

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