Page Replacement Algorithms
When memory is full, which page to evict?
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Page Replacement Algorithms
Learning Objectives
- •Learn page replacement algorithms
- •Calculate page faults
- •Understand Belady's anomaly
Lesson Outline
LearnStep 1/2
Page Replacement Algorithms
Belady's Anomaly: More frames can cause more faults!
2. Optimal (OPT)
Replace page not used for longest time (theoretical best):
3. LRU (Least Recently Used)
Replace page not used for longest time in past:
Comparison
| Algorithm | Faults | Practical? |
|---|---|---|
| FIFO | 9 | Yes, simple |
| Optimal | 6 | No (needs future) |
| LRU | 8 | Yes, common |