\"Analyzing the Round Robin Scheduling\" as seen Operating Systems - A Modern Pe
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Question
"Analyzing the Round Robin Scheduling" as seen Operating Systems - A Modern Perspective, 3rd Edition, by Gary Nutt.
In this exercise, you will study the effect of severl parameter used with RR scheduling (see Section 7.5). To solve the exercise, you will simulate the round robin scheduler. Do this by writing a simulation program to imitate the behavior of a single-CPU system that has a preemptive RR scheduler, and then collection performance data regarding the operation of the simulation. Create an input file to represent process arrival and service times, where each line represents a process arriving into your simulated system. The first number is the arrival (in integer seconds), and the second number is the amount of time the process requires to complete (in floating-point seconds). For example, the first several lines of the file might look like
Explanation / Answer
// Java program for implementation of RR scheduling
public class GFG
{
// Method to find the waiting time for all
// processes
static void findWaitingTime(int processes[], int n,
int bt[], int wt[], int quantum)
{
// Make a copy of burst times bt[] to store remaining
// burst times.
int rem_bt[] = new int[n];
for (int i = 0 ; i < n ; i++)
rem_bt[i] = bt[i];
int t = 0; // Current time
// Keep traversing processes in round-robin manner
// until all of them are not done.
while(true)
{
boolean done = true;
// Traverse all processes one by one repeatedly
for (int i = 0 ; i < n; i++)
{
// If burst time of a process is greater than 0
// then only need to process further
if (rem_bt[i] > 0)
{
done = false; // There is a pending process
if (rem_bt[i] > quantum)
{
// Increase the value of t i.e. shows
// how much time a process has been processed
t += quantum;
// Decrease the burst_time of current process
// by quantum
rem_bt[i] -= quantum;
}
// If burst time is smaller than or equal to
// quantum. Last cycle of this process
else
{
// Increase the value of t i.e. shows
// how much time a process has been processed
t = t + rem_bt[i];
// Waiting time is current time minus time
// used by this process
wt[i] = t - bt[i];
// As the process gets fully executed
// make its remaining burst time = 0
rem_bt[i] = 0;
}
}
}
// If all processes are done
if (done == true)
break;
}
}
// Method to calculate turn around time
static void findTurnAroundTime(int processes[], int n,
int bt[], int wt[], int tat[])
{
// calculating turnaround time by adding
// bt[i] + wt[i]
for (int i = 0; i < n ; i++)
tat[i] = bt[i] + wt[i];
}
// Method to calculate average time
static void findavgTime(int processes[], int n, int bt[],
int quantum)
{
int wt[] = new int[n], tat[] = new int[n];
int total_wt = 0, total_tat = 0;
// Function to find waiting time for all processes
findWaitingTime(processes, n, bt, wt, quantum);
// Function to find turn around time for all processes
findTurnAroundTime(processes, n, bt, wt, tat);
// Display processes along with all details
System.out.println("Processes " + " Burst time " +
" Waiting time " + " Turn around time");
// Calculate total waiting time and total turn
// around time
for (int i=0; i<n; i++)
{
total_wt = total_wt + wt[i];
total_tat = total_tat + tat[i];
System.out.println(" " + (i+1) + " " + bt[i] +" " +
wt[i] +" " + tat[i]);
}
System.out.println("Average waiting time = " +
(float)total_wt / (float)n);
System.out.println("Average turn around time = " +
(float)total_tat / (float)n);
}
// Driver Method
public static void main(String[] args)
{
// process id's
int processes[] = { 1, 2, 3};
int n = processes.length;
// Burst time of all processes
int burst_time[] = {10, 5, 8};
// Time quantum
int quantum = 2;
findavgTime(processes, n, burst_time, quantum);
}
}
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