مناقشة كل ما يخص (( Final M350)) لــــــــFall 2011 / 2012

[aseer k]

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Suppose that the following processes arrive for execution at the times
indicated. Each process will run the listed amount of time. In answering
the questions, use nonpreemptive scheduling and base all decisions on
the information you have at the time the decision must be made.
Process Arrival Time Burst Time
P1 0.0 8
P2 0.4 4
P3 1.0 1
a. What is the average turnaround time for these processes with the
FCFS scheduling algorithm?
13
14 Chapter 5 CPU Scheduling
b. What is the average turnaround time for these processeswith the
SJF scheduling algorithm?
c. The SJF algorithm is supposed to improve performance, but notice
that we chose to run process P1 at time 0 because we did not know
that two shorter processes would arrive soon. Compute what the
average turnaround timewill be if the CPU is left idle for the first 1
unit and then SJF scheduling is used. Remember that processes P1
and P2 arewaiting during this idle time, so their waiting timemay
increase. This algorithm could be known as future-knowledge
scheduling.
Answer:
a. 10.53
b. 9.53
c. 6.86
Remember that turnaround time is finishing time minus arrival time, so
you have to subtract the arrival times to compute the turnaround times.
FCFS is 11 if you forget to subtract arrival time

.

[Egy_Guy]

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