Consider the following page reference using four physical frames that are initially empty. (a) (5 points)...
Consider the following page reference using four physical frames that are initially empty.
(a) (5 points) Find the page faults using LRU algorithm, where the page reference sequence: 5,2,5,1,4,5,2,0,4,2,3,1,2,1,0,0,2,4,5,1?
(b) (5 points) Find the page faults using FIFO algorithm, where the page reference sequence: 5,2,1,5,1,0,3,1,2,1,4,0,5,4, 2,3,3, 4,2,1?
(c) (5 points) Find the page faults using LRU algorithm, where the page reference sequence: 5, 0, 4, 4, 0, 3, 0, 4, 1, 0, 2, 0, 5, 3, 0, 1?
Homework Answers
Consider the following page reference using four physical frames that are initially empty.
(a) Find the page faults using LRU algorithm, where the page reference sequence: 5,2,5,1,4,5,2,0,4,2,3,1,2,1,0,0,2,4,5,1?
ANSWER: (a)
The first row represents the page reference sequence
The cells with bold number denote page fault.
|
5 |
2 |
5 |
1 |
4 |
5 |
2 |
0 |
4 |
2 |
3 |
1 |
2 |
1 |
0 |
0 |
2 |
4 |
5 |
1 |
|
5 |
5 |
5 |
5 |
5 |
5 |
5 |
5 |
5 |
5 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
4 |
4 |
4 |
|
2 |
2 |
2 |
2 |
2 |
2 |
2 |
2 |
2 |
2 |
2 |
2 |
2 |
2 |
2 |
2 |
2 |
2 |
2 |
|
|
1 |
1 |
1 |
1 |
0 |
0 |
0 |
0 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
5 |
5 |
|||
|
4 |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
0 |
0 |
0 |
0 |
0 |
1 |
The number of page faults using LRU = 11
(b) Find the page faults using FIFO algorithm, where the page reference sequence: 5,2,1,5,1,0,3,1,2,1,4,0,5,4, 2,3,3, 4,2,1?
The first row represents the page reference sequence
The cells with bold number denote page fault.
ANSWER: (b)
|
5 |
2 |
1 |
5 |
1 |
0 |
3 |
1 |
2 |
1 |
4 |
0 |
5 |
4 |
2 |
3 |
3 |
4 |
2 |
1 |
|
5 |
5 |
5 |
5 |
5 |
5 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
1 |
|
2 |
2 |
2 |
2 |
2 |
2 |
2 |
2 |
2 |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
|
|
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
5 |
5 |
5 |
5 |
5 |
5 |
5 |
5 |
||
|
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
2 |
2 |
2 |
2 |
2 |
2 |
The number of page faults using FIFO = 9
(c) Find the page faults using LRU algorithm, where the page reference sequence: 5, 0, 4, 4, 0, 3, 0, 4, 1, 0, 2, 0, 5, 3, 0, 1?
ANSWER: (c)
The first row represents the page reference sequence
The cells with bold number denote page fault.
|
5 |
0 |
4 |
4 |
0 |
3 |
0 |
4 |
1 |
0 |
2 |
0 |
5 |
3 |
0 |
1 |
|
5 |
5 |
5 |
5 |
5 |
5 |
5 |
5 |
1 |
1 |
1 |
1 |
1 |
3 |
3 |
3 |
|
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
|
4 |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
5 |
5 |
5 |
5 |
||
|
3 |
3 |
3 |
3 |
3 |
2 |
2 |
2 |
2 |
2 |
1 |
The number of page faults using LRU = 9
Method to find out page fault while using LRU page replacement:
1. For each page request in the reference sequence, check whether it is already there in one of the memory frames,
3. If yes, then continue with other pages in the reference sequence.
4. If no, insert it if there is a page frame available and consider a page fault.
5. If no page frame is available, then replace the least recently used one and consider a page fault.
Method to find out page fault while using FIFO page replacement:
1. For each page request in the reference sequence, check whether it is already there in one of the memory frames,
3. If yes, then continue with other pages in the reference sequence.
4. If no, insert it if there is a page frame available and consider a page fault.
5. If no page frame is available, then replace the first inserted one and consider a page fault.
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