Consider the set of 6 processes whose arrival time and burst time are given belowIf the CPU scheduling policy is:-
1. Round Robin with time quantum = 2, calculate the average waiting time.
2. FCFS, Draw Process Gantt chart and calculate the average waiting time
3. SJF, calculate the average waiting time and calculate the average waiting time
4. Compare RR, FCFS and SJF algorithm based on average waiting time and analyze
outcome based on process synchronization.
To calculate the average waiting time, we need to first calculate the waiting time for each process. The waiting time is defined as the time period between the arrival of a process and when it starts executing.
The arrival time and burst time for the processes are as follows:
Process Arrival Time Burst Time
P1 0 3
P2 0 5
P3 1 2
P4 2 7
P5 4 4
P6 6 2
1. Round Robin with time quantum = 2:
To calculate the average waiting time for Round Robin, we simulate the scheduling algorithm. Start with the first process and assign it the CPU for time quantum 2. If the process completes within the time quantum, it is removed from the queue. If it does not complete within the time quantum, it is moved to the end of the queue and the next process is assigned the CPU.
Process Gantt Chart for Round Robin:
|P1|P2|P3|P4|P5|P6|P2|P4|P5|P4|
The '|' represents the context switch.
The waiting time for each process is as follows:
P1: 0
P2: 5
P3: 1
P4: 9
P5: 9
P6: 7
Average Waiting Time = (0 + 5 + 1 + 9 + 9 + 7) / 6 = 31 / 6 = 5.1667
2. FCFS (First-Come, First-Served):
The FCFS scheduling algorithm assigns the CPU to a process based on the order of their arrival. The process with the lowest arrival time is assigned the CPU first.
Process Gantt Chart for FCFS:
|P1|P2|P3|P4|P5|P6|
The '|' represents the context switch.
The waiting time for each process is as follows:
P1: 0
P2: 3
P3: 5
P4: 6
P5: 8
P6: 12
Average Waiting Time = (0 + 3 + 5 + 6 + 8 + 12) / 6 = 34 / 6 = 5.6667
3. SJF (Shortest Job First):
The SJF scheduling algorithm assigns the CPU to the process with the shortest burst time first.
Process Gantt Chart for SJF:
|P3|P1|P2|P5|P6|P4|
The '|' represents the context switch.
The waiting time for each process is as follows:
P1: 1
P2: 4
P3: 0
P4: 9
P5: 6
P6: 11
Average Waiting Time = (1 + 4 + 0 + 9 + 6 + 11) / 6 = 31 / 6 = 5.1667
4. Comparison and Analysis:
Based on the average waiting time:
- The Round Robin algorithm has the lowest average waiting time, followed by SJF, and then FCFS.
- Round Robin and SJF have the same average waiting time, indicating that both algorithms are fairly efficient in minimizing the waiting time.
- FCFS has the highest average waiting time, suggesting that it may not be the best choice for minimizing waiting times.
In terms of process synchronization, Round Robin and FCFS are non-preemptive algorithms, meaning that once a process is assigned the CPU, it will keep using it until it finishes or voluntarily relinquishes it. This can lead to poor utilization of the CPU if a long process is assigned the CPU first. In Round Robin, the time quantum helps to mitigate this issue by allowing other processes to have a chance to execute.
SJF is a preemptive algorithm, meaning that a process with a shorter burst time can preempt a process with a longer burst time. This can result in better CPU utilization and overall performance. However, if the burst times are not accurately estimated, it can lead to frequent context switches and overhead.
In conclusion, Round Robin and SJF are more efficient in terms of average waiting time compared to FCFS. Round Robin provides better process synchronization by allowing equal opportunities for all processes to execute, while SJF optimizes CPU utilization by prioritizing shorter burst time processes.
To answer your question, I'll need the arrival time and burst time for each of the 6 processes. Could you please provide those details?
To calculate the average waiting time for each CPU scheduling policy, we need to follow certain steps. Let's go through each of the given CPU scheduling policies and explain how to calculate the average waiting time.
1. Round Robin (RR) with Time Quantum = 2:
- In Round Robin scheduling, each process is allocated a fixed time slice called the time quantum.
- Processes are executed in a cyclic manner, each for a time quantum until all processes have been executed.
- To calculate the average waiting time, we need to calculate the waiting time of each process and then find the average of all waiting times.
- The waiting time for a process can be found by subtracting the arrival time from the sum of waiting times of the previous processes.
- The waiting time of the first process is 0, as there are no processes before it.
- We can use a formula to calculate the waiting time for each process:
- Waiting time = (Previous waiting time + Execution time of previous processes) - Arrival time
- Finally, we calculate the average waiting time by summing up all waiting times and dividing by the number of processes.
2. FCFS (First Come First Serve):
- In the FCFS scheduling policy, the process that arrives first is executed first.
- To calculate the average waiting time, we need to consider the order of process execution based on their arrival times.
- We can draw a Gantt chart to represent the process execution timeline.
- The waiting time for a process can be found by subtracting the arrival time from the start time of that process.
- The start time for the first process is its arrival time, and for subsequent processes, it is the end time of the previous process.
- Finally, we calculate the average waiting time by summing up all waiting times and dividing by the number of processes.
3. SJF (Shortest Job First):
- In the SJF scheduling policy, the process with the shortest burst time is executed first.
- To calculate the average waiting time, we need to order the processes based on their burst times.
- We then start executing the processes in the ascending order of their burst times.
- The waiting time for a process can be found by subtracting the arrival time from the start time of that process.
- The start time for the first process is its arrival time, and for subsequent processes, it is the end time of the previous process.
- Finally, we calculate the average waiting time by summing up all waiting times and dividing by the number of processes.
4. Comparing RR, FCFS, and SJF Algorithm:
- Once we have calculated the average waiting time for each scheduling policy, we can compare and analyze the outcomes.
- The policy with the lowest average waiting time is considered better, as it indicates less waiting time for processes.
- Based on the comparison of average waiting times, we can analyze the performance of each algorithm in terms of process synchronization.
- RR ensures fairness by allocating fixed time slices to each process, giving equal opportunities to execute.
- FCFS does not prioritize short processes, which may cause longer waiting times for processes with longer burst times.
- SJF prioritizes short processes, reducing their waiting times, but it may lead to starvation for long processes.
- The analysis of process synchronization helps us understand the impact of each algorithm on the overall efficiency and fairness of task execution.
By following these steps and calculations, you will be able to answer the questions and analyze the outcomes based on the average waiting time and process synchronization for each CPU scheduling policy.