A LRU page replacement is used with 4 page frames and eight pages. How many…

Solution: Simulate the LRU policy with 4 empty frames for the reference string 0 1 7 2 3 2 7 1 0 3.

1. Reference 0: miss — load 0. Frames: [0]. Faults = 1.

2. Reference 1: miss — load 1. Frames: [0, 1]. Faults = 2.

3. Reference 7: miss — load 7. Frames: [0, 1, 7]. Faults = 3.

4. Reference 2: miss — load 2. Frames: [0, 1, 7, 2]. Faults = 4.

5. Reference 3: miss — evict least recently used page 0; load 3. Frames: [3, 1, 7, 2]. Faults = 5.

6. Reference 2: hit (2 is in frames). Faults = 5.

7. Reference 7: hit (7 is in frames). Faults = 5.

8. Reference 1: hit (1 is in frames). Faults = 5.

9. Reference 0: miss — evict least recently used page 3; load 0. Frames: [0, 1, 7, 2]. Faults = 6.

10. Reference 3: miss — evict least recently used page 2; load 3. Frames: [0, 1, 7, 3]. Faults = 7.

Total page faults = 7.

Therefore the correct answer is 7 page faults.