Develop a Gantt Chart, Average Waiting time, FCFS, SJF, RR

RGPV 2020 CPU Scheduling Algorithm

Consider the following set of processes.

Process	Burst Time	Arrival Time
P1	3	0
P2	5	1
P3	2	2
P4	5	3
P5	5	4

Develop a Gantt-chart and calculate the average waiting time using:

i) FCFS

ii) SJF

iii) Round Robin (q = 1)

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GATE 1996 CPU Scheduling algo completion time RR

GATE 1996

Four jobs to be executed on a single processor  system arrive at time 0+ in the order A, B, C, D.  Their burst CPU time requirements are 4,1, 8, 1  time units respectively. The completion time of  A under round robin scheduling with time slice  of one time unit is  

(a) 10 

(b) 4  

(c) 8 

(d) 9

Sol. 

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GATE 2006 CPU scheduling PYQ

GATE 2006

The arrival time, priority, and durations of the  CPU and I/O bursts for each of three processes  P1, P2 and P3 are given in the table below. Each  process has a CPU burst followed by an I/O burst  followed by another CPU burst. Assume that each  process has its own I/O resource. 

Process	Arrival Time	Priority	Burst Duration
			CPU	I/O	CPU
P1	0	2	1	5	3
P2	2	3 (lowest)	3	3	1
P3	3	1 (highest)	2	3	1

The multi-programmed operating system uses  preemptive priority scheduling. What are the  finish times of the processes P1, P2 and P3?  

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GATE 2005 CPU scheduling PYQ

GATE 2005

We wish to schedule three processes P1, P2 and  P3 on a uniprocessor system. The priorities, CPU  time requirements and arrival times of the  processes are as shown below. 

Process	Priority	CPU Time Required	Arrival Time (hh : mm : ss)
P1	10 (highest)	20 sec	00:00:05
P2	9	10 sec	00:00:03
P3	8 (lowest)	15 sec	00:00:00

We have a choice of preemptive or nonpreemptive scheduling. In preemptive scheduling,  a late-arriving higher priority process can  preempt a currently running process with lower  priority. In non-preemptive scheduling, a latearriving higher priority process must wait for the  currently executing process to complete before it  can be scheduled on the processor. What are the  turnaround times (time from arrival tili  completion) of P2 using preemptive and nonpreemptive scheduling respectively? 

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GATE 2004 CPU scheduling PYQ

GATE 2004

Consider the following set of processes, vvith the  arrival times and the CPU-burst times given in  milliseconds 

Process	Arrival Time	Burst Time
P1	0	5
P2	1	3
P3	2	3
P4	4	1

What is the average turnaround time for these  processes vvith the preemptive Shortest  Remaining Processing Time first (SRPT)  algorithm? 

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GATE CPU scheduling PYQ

GATE PYQ

Q. The sequence ........ is an optimal non-preemptive  scheduling sequence for the following jobs which  leaves the CPU idle for........ unit(s) of time.  

Job	Arrival Time	Burst Time
1	0.0	9
2	0.6	5
3	1.0	1

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GATE CS 2020 CPU Scheduling PYQ

GATE 2020

Q50. Consider the following set of processes, assumed to have arrived at time 0. Consider the CPU scheduling algorithms Shortest Job First (SJF) and Round Robin (RR). For RR, assume that the processes are scheduled in the order P!, P2, P3, P4.

Processes	P1	P2	P3	P4
Burst time (in ms)	8	7	2	4

If the time quantum for RR is 4 ms, then the absolute value of the difference between the average turn around times (in ms) of SJF and RR (round off to 2 decimal places) is _____________________.

Solution.

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GATE CPU scheduling PYQ

GATE 1998

State an undesirable characteristic of each of the  following criteria for measuring performance of  an operating system:  

(a) Turn around time  

(b) Waitingtime

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