[Solved] If the time quantum is set equal to the longest CPU burst among all processes in Round Robin scheduling, what is the expected impact on turnaround time and fairness? | Operating Systems

Operating Systems - Round Robin Scheduling - Quantum & Turnaround Time

If the time quantum is set equal to the longest CPU burst among all processes in Round Robin scheduling, what is the expected impact on turnaround time and fairness?

ABoth turnaround time and fairness improve because processes get longer uninterrupted CPU bursts

BTurnaround time approaches that of First-Come-First-Serve scheduling, but fairness among processes decreases

CFairness remains the same but turnaround time increases due to longer waiting times

DTurnaround time decreases significantly and fairness improves due to fewer context switches

Step-by-Step Solution

Step 1: Understand quantum equal to longest burst
Setting quantum to longest burst means processes run mostly to completion without preemption.
Step 2: Compare to FCFS
This behavior mimics FCFS, where processes run in arrival order without interruption.
Step 3: Analyze fairness and turnaround
Fairness decreases because shorter processes wait longer, losing RR's time-sharing benefit. Turnaround time approaches FCFS values.
Step 4: Evaluate incorrect options
Turnaround time decreases significantly and fairness improves due to fewer context switches is wrong because fewer context switches do not improve fairness. Fairness remains the same but turnaround time increases due to longer waiting times is wrong as fairness changes. Both turnaround time and fairness improve because processes get longer uninterrupted CPU bursts is wrong because fairness does not improve.
Final Answer:
Option B -> Option B
Quick Check:
Quantum = longest burst -> RR ≈ FCFS -> fairness ↓, turnaround ~ FCFS.

Quick Trick: Quantum = longest burst -> RR behaves like FCFS

Common Mistakes:

MISTAKES

Assuming fairness always improves with larger quantum
Believing fewer context switches always reduce turnaround
Ignoring that RR degenerates to FCFS with large quantum

Trap Explanation:

PITFALL

Option B is tempting due to fewer context switches, but fairness suffers. Option D incorrectly assumes longer bursts improve fairness.

Interviewer Note:

CONTEXT

Tests deep understanding of quantum size impact on RR behavior and its convergence to FCFS.

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Solution Trace

More Operating Systems Quizzes

If the time quantum is set equal to the longest CPU burst among all processes in Round Robin scheduling, what is the expected impact on turnaround time and fairness?

Step 1: Understand quantum equal to longest burst

Step 2: Compare to FCFS

Step 3: Analyze fairness and turnaround

Step 4: Evaluate incorrect options

Final Answer:

Quick Check:

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