Preemptive Scheduling
Preemptive Scheduling (Round Robin) problems involve scheduling processes where each process runs for a fixed time quantum before being preempted. You need to calculate average completion time or turnaround time.
What You'll Learn
Introduction to Preemptive Scheduling
Preemptive Scheduling (Round Robin) problems involve scheduling processes where each process runs for a fixed time quantum before being preempted. You need to calculate average completion time or turnaround time.
Prerequisites
How to Solve Preemptive Scheduling Problems
Step 1: List processes with burst times
Step 2: Set time quantum (Q)
Step 3: Simulate Round Robin: each process runs for Q or until completion
Step 4: Track completion time for each process
Step 5: Calculate average completion time = sum(completion times) / n
Step 6: Answer with average
Example Problem
Example: Processes: P1(5), P2(3), P3(4). Time quantum = 2. Average completion time? Solution: Step 1: Order: P1(2), P2(2), P3(2), P1(2), P2(1), P3(2), P1(1) Step 2: Timeline: 0-2(P1),2-4(P2),4-6(P3),6-8(P1),8-9(P2),9-11(P3),11-12(P1) Step 3: Completion: P1=12, P2=9, P3=11 Step 4: Average = (12+9+11)/3 = 32/3 = 10.67 Answer: 10.67
Pro Tips & Tricks
- Round Robin: each process gets Q time, then next in queue
- If burst < Q, process completes and leaves
- New processes go to end of queue
- Completion time = last time process runs
Shortcut Methods to Solve Faster
Common Mistakes to Avoid
Practice Worksheets
Practice makes perfect! Work through these worksheets to master Preemptive Scheduling. Each worksheet contains 20 questions with detailed explanations. Start from Worksheet 1 and progress through increasing difficulty levels.
Exam Importance
Preemptive Scheduling is an important topic for various competitive exams. Here's how frequently it appears:
Ready to Master Preemptive Scheduling?
Start with Worksheet 1 and work your way up to expert level! Each worksheet includes: