Question

Name Olbinna COSC414/514 Quiz3 (1) Suppose a computer has 4 physical pages, and a process references its virtual pages (page o through page 7) in the following order: 021354637473355311172341 Also suppose the first four pages have been loaded in the physical memory as the following figure: Frame 0 Frame 1 Frame 2 Frame 3 a. Suppose the kernel uses First-In-First-Out (FIFO) page replacement algorithm. How many page faults would the process have? Which page references are page faults? b. Suppose the kemel uses Least-Recently-Used (LRU) algorithm for page replacement, answer the above two questions. c. Suppose the kernel uses the optimal page replacement algorithm (i.e. replace pages that will not be used for longest period of time), answer the above two questions. 2) Discuss the difference between external and internal fragmentation (6) Discuss the advantages and disadvantages of large page size vs. small page size (4) Why is frequency of page usage a poor measure for reducing future page faults? (5) Which page-replacement strategy incurs more execution overhead: least recent used (LRU) or least frequently used (LFU)?

Answer 1

Solution

a)

0 2 1 3 5 4 6 3 7 4 7 3 3 5 5 3 1 1 1 7 2 3 4 1

FIFO

0	5	5	5	5	3	3	3	3	4
2	2	4	4	4	4	5	5	5	5
1	1	1	6	6	6	6	1	1	1
3	3	3	3	7	7	7	7	2	2

4 1 1 1 1 1 1 1 1 1

Total Number of Page fault is 13

B)

LRU

0	5	5	5	7	7	7	7	7	1
2	2	4	4	4	4	1	1	4	4
1	1	1	6	6	5	5	2	2	2
3	3	3	3	3	3	3	3	3	3

4 1 1 1 1 1 1 1 1 1

Total Number of Page fault is 13

C)Optimal

OPTIMAL

0	5	5	5	5	1	1
2	2	4	4	4	4	4
1	1	1	6	7	7	2
3	3	3	3	3	3	3

4 1 1 1 1 1 1

Total Number of Page fault is 10

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