Consider a system running ten I/O-bound tasks and one CPU-bound task. Assume tha
ID: 3833719 • Letter: C
Question
Consider a system running ten I/O-bound tasks and one CPU-bound task. Assume that the I/O-bound tasks issue an I/O operation once for every millisecond of CPU computing and that each I/O operation takes 10 milliseconds to complete. Also assume that the context-switching overhead is 0.1 millisecond and that all processes are long-running tasks Describe is the CPI utilization for a round-robin scheduler when. a. The time quantum is 1 millisecond b. The time quantum is 10 milliseconds The following processes are being scheduled using: 1) a preemptive. round robin scheduling algorithm (RR), 2) FCFS, 3) SJF, 4) Non preemptive priority. Each process is assigned a numerical priority, with a higher number indicating a higher relative priority in addition to the processes listed below, the system also has an idle task (which consumes no CPU resources and is identified as P idle). This task has priority 0 and is scheduled whenever the system has no other available processes to run. The length of a time quantum is 10 units. If a process is preempted by a higher-priority process, the preempted placed at the end of the queue process is placed at the end of the queue. a. Show the scheduling order of the processes using a Gantt chart for all 4 schedules. b What is the turnaround time for each process for each scheduling strategy? c. What is the waiting time for each process for each scheduling strategy?Explanation / Answer
Answer:
a)The time quantum is 1 millisecond:
i. CPU utilization of the tasks 1ms 11 = 11ms
ii. Every task will use up the whole quantum. The I/O operations for the I/O bound tasks will return in time for their next turn. Only non utilizations will be the context switch 11 .1 = 1.1ms.
iii. 1.1ms + 11ms = 12.1ms total time.
iv. 11/12.1 = .909, 90.9%
b) The time quantum is 10 millisecond:
i. Total time (1ms + .1ms) 10 + 10 + .1 = 21.1
ii. CPU utilization of CPU-bound task = 10ms
iii. CPU utilization of I/O bound tasks = 1ms then context switch
iv. 1 10 + 10 = 20ms total CPU utilization v. 20/21.1 = .9478, 94.78%
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