1. Review Questions on Chapter III—Scheduling COSC 4330/6310 Summer 2013

2. First Question  In the Round Robin policy, what the advantages and disadvantages of selecting a small time quantum? (2×5 points)

3. First Question  In the Round Robin policy, what the advantages and disadvantages of selecting a small time quantum? (2×5 points) The main advantage of small time slices is a faster response time for interactive requests The main advantage of small time slices is a faster response time for interactive requests

4. First Question  In the Round Robin policy, what the advantages and disadvantages of selecting a small time quantum? (2×5 points) The main advantage of small time slices is a faster response time for interactive requests The main advantage of small time slices is a faster response time for interactive requests Their main disadvantage is too much CPU time taken by context switches Their main disadvantage is too much CPU time taken by context switches

5. Second Question  Consider the following set of parameters for a System V Release 4 scheduler with four priority levels: #ts_quantum ts_tqexp ts_slpret ts_maxwait ts_lwait LVL 800 X 1 1000 1 # 0 800 X 1 1000 1 # 0 400 0 2 1000 2 # 1 400 0 2 1000 2 # 1 200 1 3 200 3 # 2 200 1 3 200 3 # 2 100 2 Y 200 3 # 3 100 2 Y 200 3 # 3  Which are the sole reasonable values for X and Y? X=__ and Y= __X=__ and Y= __

6. Second Question  Consider the following set of parameters for a System V Release 4 scheduler with four priority levels: #ts_quantum ts_tqexp ts_slpret ts_maxwait ts_lwait LVL 800 X 1 1000 1 # 0 800 X 1 1000 1 # 0 400 0 2 1000 2 # 1 400 0 2 1000 2 # 1 200 1 3 200 3 # 2 200 1 3 200 3 # 2 100 2 Y 200 3 # 3 100 2 Y 200 3 # 3  Which are the sole reasonable values for X and Y? X=_0_ and Y= __X=_0_ and Y= __

7. Second Question  Consider the following set of parameters for a System V Release 4 scheduler with four priority levels: #ts_quantum ts_tqexp ts_slpret ts_maxwait ts_lwait LVL 800 X 1 1000 1 # 0 800 X 1 1000 1 # 0 400 0 2 1000 2 # 1 400 0 2 1000 2 # 1 200 1 3 200 3 # 2 200 1 3 200 3 # 2 100 2 Y 200 3 # 3 100 2 Y 200 3 # 3  Which are the sole reasonable values for X and Y? X=_0_ and Y= _3_X=_0_ and Y= _3_

8. Third Question  Consider the following System V Release 4 scheduler: #ts_quantum ts_tqexp ts_slpret ts_maxwait ts_lwait LVL 800 0 1 16000 0 # 0 800 0 1 16000 0 # 0 400 0 2 8000 2 # 1 400 0 2 8000 2 # 1 200 2 3 4000 3 # 2 200 2 3 4000 3 # 2 100 2 4 2000 4 # 3 100 2 4 2000 4 # 3  and identify the four incorrect parameters: (4×5 points)

9. Third Question  Consider the following System V Release 4 scheduler: #ts_quantum ts_tqexp ts_slpret ts_maxwait ts_lwait LVL 800 0 1 16000 0 # 0 800 0 1 16000 0 # 0 400 0 2 8000 2 # 1 400 0 2 8000 2 # 1 200 2 3 4000 3 # 2 200 2 3 4000 3 # 2 100 2 4 2000 4 # 3 100 2 4 2000 4 # 3  and identify the four incorrect parameters: (4×5 points)

10. Third Question  Consider the following System V Release 4 scheduler: #ts_quantum ts_tqexp ts_slpret ts_maxwait ts_lwait LVL 800 0 1 16000 0 # 0 800 0 1 16000 0 # 0 400 0 2 8000 2 # 1 400 0 2 8000 2 # 1 200 2 3 4000 3 # 2 200 2 3 4000 3 # 2 100 2 4 2000 4 # 3 100 2 4 2000 4 # 3  and identify the four incorrect parameters: (4×5 points)

11. Third Question  Consider the following System V Release 4 scheduler: #ts_quantum ts_tqexp ts_slpret ts_maxwait ts_lwait LVL 800 0 1 16000 0 # 0 800 0 1 16000 0 # 0 400 0 2 8000 2 # 1 400 0 2 8000 2 # 1 200 2 3 4000 3 # 2 200 2 3 4000 3 # 2 100 2 4 2000 4 # 3 100 2 4 2000 4 # 3  and identify the four incorrect parameters: (4×5 points)

12. Third Question  Consider the following System V Release 4 scheduler: #ts_quantum ts_tqexp ts_slpret ts_maxwait ts_lwait LVL 800 0 1 16000 0 # 0 800 0 1 16000 0 # 0 400 0 2 8000 2 # 1 400 0 2 8000 2 # 1 200 2 3 4000 3 # 2 200 2 3 4000 3 # 2 100 2 4 2000 4 # 3 100 2 4 2000 4 # 3  and identify the four incorrect parameters: (4×5 points)

13. Fourth Question  Consider the following System V Release 4 scheduler: (3×5 points) #ts_quantum ts_tqexp ts_slpret ts_maxwait ts_lwait LVL 1000 0 1 16000 1 # 0 1000 0 1 16000 1 # 0 500 1 2 8000 2 # 1 500 1 2 8000 2 # 1 200 1 3 4000 3 # 2 200 1 3 4000 3 # 2 100 2 3 2000 3 # 3 100 2 3 2000 3 # 3 Which events can increase the priority of a process at level 2? Which events can increase the priority of a process at level 2? Which events can lower it? Which events can lower it?

14. Fourth Question  Consider the following System V Release 4 scheduler: (3×5 points) #ts_quantum ts_tqexp ts_slpret ts_maxwait ts_lwait LVL 1000 0 1 16000 1 # 0 1000 0 1 16000 1 # 0 500 1 2 8000 2 # 1 500 1 2 8000 2 # 1 200 1 3 4000 3 # 2 200 1 3 4000 3 # 2 100 2 3 2000 3 # 3 100 2 3 2000 3 # 3 A return from the wait state or a long wait in the ready queue will increase the priority of a process A return from the wait state or a long wait in the ready queue will increase the priority of a process

15. Fourth Question  Consider the following System V Release 4 scheduler: (3×5 points) #ts_quantum ts_tqexp ts_slpret ts_maxwait ts_lwait LVL 1000 0 1 16000 1 # 0 1000 0 1 16000 1 # 0 500 1 2 8000 2 # 1 500 1 2 8000 2 # 1 200 1 3 4000 3 # 2 200 1 3 4000 3 # 2 100 2 3 2000 3 # 3 100 2 3 2000 3 # 3 A return from the wait state or a long wait in the ready queue will increase the priority of a process A return from the wait state or a long wait in the ready queue will increase the priority of a process A CPU timer interrupt will decrease it A CPU timer interrupt will decrease it

16. Short Questions  What is the major limitation of the round- robin scheduling policy?

17. Short Questions  What is the major limitation of the round- robin scheduling policy? RR cannot provide at the same time a good interactive response time and a good throughput at medium to heavy load RR cannot provide at the same time a good interactive response time and a good throughput at medium to heavy load

18. Short Questions  What is the main advantage of preemptive schedulers over non- preemptive ones?

19. Short Questions  What is the main advantage of preemptive schedulers over non- preemptive ones? Scheduler can take CPU way from processes "monopolizing" the CPU Scheduler can take CPU way from processes "monopolizing" the CPU Other processes do not have to wait as longOther processes do not have to wait as long

20. Short Questions  What do schedulers typically do to increase the priorities of I/O-bound processes?

21. Short Questions  What do schedulers typically do to increase the priorities of I/O-bound processes? They increase the priorities of processes returning to the ready queue from the wait state They increase the priorities of processes returning to the ready queue from the wait state Very likely to have performed an I/OVery likely to have performed an I/O

22. Short Questions  What do schedulers typically do to lower the priorities of CPU-bound processes?

23. Short Questions  What do schedulers typically do to lower the priorities of CPU-bound processes? They decrease the priority of processes who have been preempted because they have exhausted their CPU time slice They decrease the priority of processes who have been preempted because they have exhausted their CPU time slice

24. True or False  The Round-Robin scheduling algorithm does not differentiate between CPU- bound and I/O-bound processes.

25. True or False  The Round-Robin scheduling algorithm does not differentiate between CPU- bound and I/O-bound processes. TRUE because all processes have the same priority TRUE because all processes have the same priority

26. True or False  The Round-Robin scheduling algorithm is starvation-free.

27. True or False  The Round-Robin scheduling algorithm is starvation-free. TRUE because all processes have the same priority TRUE because all processes have the same priority

28. True or False  Most schedulers adjust the priorities of real-time processes in order to give each process its fair share of the CPU.

29. True or False  Most schedulers adjust the priorities of real-time processes in order to give each process its fair share of the CPU. FALSE, the schedulers we have discussed assign fixed priorities to real-time processes FALSE, the schedulers we have discussed assign fixed priorities to real-time processes

30. True or False  Steps taken to decrease the response time of a system can sometimes decrease its throughput.

31. True or False  Steps taken to decrease the response time of a system can sometimes decrease its throughput. TRUE, think of the round-robin policy TRUE, think of the round-robin policy

32. True or False  All preemptive policies have multiple priority levels.

33. True or False  All preemptive policies have multiple priority levels. TRUE, think of the round-robin policy TRUE, think of the round-robin policy

34. True or False  The throughput of a computer using a round-robin scheduling policy often goes down when the number of users goes up.

35. True or False  The throughput of a computer using a round-robin scheduling policy often goes down when the number of users goes up.. TRUE because the context switch overhead is likely to increase TRUE because the context switch overhead is likely to increase