A computer has 16 pages of virtual address space but the size of main memory…
2014
A computer has 16 pages of virtual address space but the size of main memory is only four frames. Initially the memory is empty. A program references the virtual pages in the order 0, 2, 4, 5, 2, 4, 3, 11, 2, 10. How many page faults occur if LRU page replacement algorithm is used?
- A.
3
- B.
5
- C.
7
- D.
8
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Correct answer: C
We simulate LRU with 4 frames on reference string: 0, 2, 4, 5, 2, 4, 3, 11, 2, 10. 1. 0: Fault (Mem: [0]) 2. 2: Fault (Mem: [0, 2]) 3. 4: Fault (Mem: [0, 2, 4]) 4. 5: Fault (Mem: [0, 2, 4, 5]) 5. 2: Hit (LRU: 0) 6. 4: Hit (LRU: 2) 7. 3: Fault (Replace 0) -> Mem: [5, 2, 4, 3] 8. 11: Fault (Replace 5) -> Mem: [2, 4, 3, 11] 9. 2: Hit (LRU: 4) 10. 10: Fault (Replace 4) -> Mem: [3, 11, 2, 10] Total faults: 7.
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