Chapter 9: Uniprocessor Scheduling

Transcription

1 Chapter 9: Uniprocessor Scheduling

2 Scheduling Long-term Admit a new process Medium-term Suspend a process Short-term Block/preempt running process I/O scheduling

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5 Scheduling criteria

6 Criteria User-oriented Turn-around time Response time Deadlines Predictability System-oriented Throughput CPU utilization Fairness Priorities Resource balancing

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8 Priority inversion

9 Priority inversion 30 running

10 Priority inversion 30 running acquire lock A

11 Priority inversion 30 running ready acquire lock A HI begins 50 running

12 Priority inversion 30 running ready acquire lock A HI begins HI tries to acquire lock A 50 running

13 Priority inversion running ready acquire lock A HI begins HI tries to acquire lock A 50 blocked running

14 Priority inversion running ready acquire HI release 50 lock A begins lock A blocked running HI tries to acquire lock A

15 Priority inversion 30 running ready acquire HI release 50 lock A begins lock A running HI tries to acquire lock A

16 Priority inversion 30 running ready acquire HI release 50 lock A begins lock A running HI tries to acquire lock A thread exit

17 Priority inversion 30 running acquire lock A HI begins release lock A HI tries to acquire lock A thread exit

18 Priority donation Multiple L (A), (B) => M [A] => H [B] Nested L (A) => M (B), [A] => H [B] Chained L (A) => M [A] => H [A]

19 Policies FCFS Round robin Shortest process next Shortest remaining time Highest response ratio next Feedback

20 FCFS Nonpreemptive, first-come, first-served

21 FCFS Nonpreemptive, first-come, first-served

22 FCFS Nonpreemptive, first-come, first-served A B C D E Mean Finish Time TAT (Tr) Tr/Ts

23 FCFS Nonpreemptive, first-come, first-served A B C D E Mean Finish Time TAT (Tr) Tr/Ts

24 RR Preemptive...add current to end of queue, FCFS for all others

25 RR Preemptive...add current to end of queue, FCFS for all others

26 RR Preemptive...add current to end of queue, FCFS for all others A B C D E Mean Finish Time TAT (Tr) Tr/Ts

27 RR Preemptive...add current to end of queue, FCFS for all others A B C D E Mean Finish Time TAT (Tr) Tr/Ts

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30 SPN Nonpreemptive...others FCFS

31 SPN Nonpreemptive...others FCFS

32 SPN Nonpreemptive...others FCFS A B C D E Mean Finish Time TAT (Tr) Tr/Ts

33 SPN Nonpreemptive...others FCFS A B C D E Mean Finish Time TAT (Tr) Tr/Ts

34 Exponential averaging

35 SRT Preemptive...FCFS for same remaining time

36 SRT Preemptive...FCFS for same remaining time

37 SRT Preemptive...FCFS for same remaining time A B C D E Mean Finish Time TAT (Tr) Tr/Ts

38 SRT Preemptive...FCFS for same remaining time A B C D E Mean Finish Time TAT (Tr) Tr/Ts

39 HRRN

40 HRRN

41 HRRN A B C D E Mean Finish Time TAT (Tr) Tr/Ts

42 Feedback Processes start in RQ0 Move one queue lower at each preemption FCFS within ready queues Process in RQi can execute for q units (q = 1 or 2 i units)

43 Feedback

44 Feedback

45 Feedback A B C D E Mean Finish Time TAT (Tr) Tr/Ts

46 Feedback A B C D E Mean Finish Time TAT (Tr) Tr/Ts

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48 Fair-share scheduling Give each user a fair share Process groups get equal proportion Scheduling is priority based

49 Fair-share scheduling Give each user a fair share Process groups get equal proportion Scheduling is priority based CPU j(i - 1) CPUj(i) = 2 GCPU k(i - 1) GCPUk(i) = 2

50 Fair-share scheduling Give each user a fair share Process groups get equal proportion Scheduling is priority based CPU j(i - 1) CPUj(i) = 2 GCPU k(i - 1) GCPUk(i) = 2 Pj(i) = Basej + CPUj(i) + GCPU k(i) 2 4 * Wk

51 Fair-share scheduling Give each user a fair share Process groups get equal proportion Scheduling is priority based CPU j(i - 1) CPUj(i) = 2 GCPU k(i - 1) GCPUk(i) = 2 Pj(i) = Basej + CPUj(i) + GCPU k(i) 2 4 * Wk nice in traditional UNIX

52 CPU j(i - 1) CPUj(i) = 2 GCPU k(i - 1) GCPUk(i) = 2 CPU j(i) Pj(i) = Basej + 2 GCPU k(i) + 4 * W k