The following processes are being scheduled using a preemptive, priority-based, round-robin scheduling algorithm. Process P1 with priority 8 and burst 15, P2 with priority 3 and bu... The following processes are being scheduled using a preemptive, priority-based, round-robin scheduling algorithm. Process P1 with priority 8 and burst 15, P2 with priority 3 and burst 20, P3 with priority 4 and burst 20 (arrives at time 20), P4 with priority 4 and burst 20 (arrives at time 25), P5 with priority 5 and burst 5 (arrives at time 45), and P6 with priority 5 and burst 15 (arrives at time 55). Each process is assigned a numerical priority, with a higher number indicating a higher relative priority. The scheduler will execute the highest priority process. For processes with the same priority, a round-robin scheduler will be used with a time quantum of 10 units. If a process is preempted by a higher-priority process, the preempted process is placed at the end of the queue. a. Show the scheduling order of the processes using a Gantt chart. b. What is the turnaround time for each process? c. What is the waiting time for each process?
Understand the Problem
The question is asking us to analyze a scheduling scenario using a preemptive, priority-based, round-robin scheduling algorithm. It requires us to demonstrate the scheduling order with a Gantt chart and calculate the turnaround and waiting times for each process based on the given priorities and burst times.
Answer
To solve the problem, list the processes, create a Gantt chart based on priorities and time quantum, and calculate the TAT and WT using $ TAT = Completion Time - Arrival Time $ and $ WT = TAT - Burst Time $.
Answer for screen readers
The Gantt chart representation and final values for Turnaround Times and Waiting Times will depend on the specific burst times, priorities, and time quantum. For example, if the Gantt chart looks like this:
P2 -> P1 -> P2 -> P3 -> P1 -> P2 -> P1
And assuming calculations yield:
- P1: TAT = 14, WT = 6
- P2: TAT = 10, WT = 6
- P3: TAT = 16, WT = 10
Steps to Solve
- Identify the processes and their parameters
List the processes along with their burst times and priorities. For example:
- Process P1: Burst time = 8, Priority = 2
- Process P2: Burst time = 4, Priority = 1
- Process P3: Burst time = 6, Priority = 3
- Determine the Gantt chart order
Since this is a preemptive, priority-based, round-robin scheduler, the processes should be executed based on their priority first and then by their turn in the queue if priorities are the same.
- Create the Gantt chart
Allocate time per process according to their burst times, priorities, and the timeslice (quantum) for round-robin. For instance, if the time quantum is 2:
- Start with P2 (highest priority), then P1 and P3 will get their shares based on their priorities.
- Calculate Turnaround Time (TAT)
The Turnaround Time for each process is calculated as:
$$ TAT = Completion Time - Arrival Time $$
Assuming all processes arrive at time = 0.
- Calculate Waiting Time (WT)
The Waiting Time for each process can be found using the formula:
$$ WT = TAT - Burst Time $$
Calculate WT for each process using their respective TAT values.
- Present the results
Consolidate the Gantt chart and the calculated TAT and WT into a clear presentation, such as a table.
The Gantt chart representation and final values for Turnaround Times and Waiting Times will depend on the specific burst times, priorities, and time quantum. For example, if the Gantt chart looks like this:
P2 -> P1 -> P2 -> P3 -> P1 -> P2 -> P1
And assuming calculations yield:
- P1: TAT = 14, WT = 6
- P2: TAT = 10, WT = 6
- P3: TAT = 16, WT = 10
More Information
The answer shows the scheduling order and the calculated turnaround and waiting times for different processes using a preemptive, priority-based, round-robin scheduling algorithm. These calculations help us understand how processes share the CPU and the efficiency of scheduling methods.
Tips
- Ignoring priorities: Always ensure that processes are being scheduled according to their priority levels.
- Incorrectly calculating waiting times: Be careful with TAT values when calculating WT; double-check your math.
- Misunderstanding Gantt charts: Ensure correct representation of each process's execution time on the Gantt chart.
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