Real-Time Operating Systems

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Jackson’s algorithm (3) ¿ Example of feasible schedule: ¿ Example of unfeasible schedule: 51 Horn’s algorithm ¿ 1 | preem| L max ¿ Principle: Earliest Deadline First (EDF) ¿ It can be proved that: ¿ Given a set of n independent tasks with arbitrary arrival times, any algorithm that at any instant executes the task with the earliest absolute deadline among all the ready tasks is optimal with respect to minimizing the maximum lateness. ¿ Complexity: ¿ per task: inserting a newly arriving task into an ordered list properly: ¿ n tasks => total complexity O(n 2 ) ¿ Non preemptive EDF is not optimal! 52 26
Horn’s algorithm ¿ Example: 53 Scheduling with precedence constraints ¿ In General: NP-hard problem ¿ For special cases polynomial time algorithms possible ¿ Two schemes: ¿ Latest Deadline First (LDF) ¿ Modified EDF 54 27
Page 1 and 2: Real-Time Operating Systems 1 Summa
Page 3 and 4: ¿ Real-time Introduction (3) ¿ Ti
Page 5 and 6: RTOS 9 Real-time Operating Systems
Page 7 and 8: Real-time Operating Systems (3) ¿
Page 9 and 10: Achieving predictability: interrupt
Page 11 and 12: Priority inversion (2) ¿ Basic pri
Page 13 and 14: Achieving predictability: memory ma
Page 15 and 16: Processes ¿ Called tasks in the RT
Page 17 and 18: Scheduling constraints ¿ The follo
Page 19 and 20: Periodic and aperiodic tasks ¿ Per
Page 21 and 22: Real-time scheduling 41 ¿ Given: S
Page 23 and 24: Scheduling metrics ¿ n tasks ¿ Av
Page 25: Jackson’s algorithm [1955] ¿ 1 |
Page 29 and 30: Introduction ¿ Periodic activities
Page 31 and 32: Processor utilization factor (2) ¿
Page 33 and 34: Cyclic executive approach ¿ Schedu
Page 35 and 36: Process-based scheduling ¿ Fixed-p
Page 37 and 38: RM schedulability test (2) ¿ For l
Page 39 and 40: EDF algorithm ¿ Dynamic scheduling
Page 41 and 42: Deadline monotonic (DM) scheduling
Page 43 and 44: EDF for D
Page 45 and 46: Periodic task scheduling: summary D

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