Operating Systems - Page Replacement - FIFO, LRU, Optimal Algorithm
Consider a system using LRU page replacement with 3 frames and the reference string: 7, 0, 1, 2, 0, 3, 0. How many page faults occur?
Consider a system using LRU page replacement with 3 frames and the reference string: 7, 0, 1, 2, 0, 3, 0. How many page faults occur?
easy🧠🧾 Concept Trace Q3 of Q15
Step-by-Step Solution
Solution:
Step 1: Trace page faults step-by-step
Frames empty initially. Insert 7 (fault 1), 0 (fault 2), 1 (fault 3). Next 2 replaces 7 (fault 4). Next 0 is hit. Next 3 replaces 1 (fault 5). Next 0 is hit. Total faults = 6.Final Answer:
Option C -> Option CQuick Check:
Counting faults carefully yields 6 [OK]
Quick Trick: Count faults only on misses, track LRU correctly [OK]
Common Mistakes:
MISTAKES- Counting hits as faults
- Misidentifying which page is least recently used
- Off-by-one errors in counting faults
Trap Explanation:
PITFALL- Candidates often confuse hits with faults or misapply LRU order, leading to wrong counts.
Interviewer Note:
CONTEXT- Tests verbal tracing and understanding of LRU behavior.
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