Page replacement algorithm
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The document discusses various page replacement algorithms aimed at achieving the lowest page-fault rate, specifically FIFO, LRU, and Optimal algorithms. Each algorithm is illustrated with examples and reference strings, detailing how page faults are calculated and the frames involved. The FIFO and LRU algorithms both recorded 8 page faults in their examples, while the Optimal algorithm recorded 6 page faults.
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Page replacement algorithm
- 1. Topic:- Presented By- Lavina Gehlot B.C.A 2nd YEAR
- 2. Page Replacement : Want lowest page-fault rate Evaluate algorithm by running it on a particular string of memory references & computing the number of page faults & page replacement on that string.
- 3. Page Replacement Algorithm FIFO Page Replacement Algorithm LRU Page Replacement Algorithm Optimal Page Replacement Algorithm
- 4. First In First Out Algorithm Replace that block in the set that has been in the cache for longest period of time FIFO Example Reference String is : 1,2,5,3,2,4,5,1,2,6 Frame Size=3 1 1 1 3 3 3 3 3 2 2 2 2 2 2 4 4 4 4 6 5 5 5 5 5 1 1 1 Page Fault : 8
- 5. Least Recently Used Algorithm Replace that block in the set that has been in the cache for longest period of time with no reference to it LRU Example Reference String is : 5,1,2,3,2,4,5,1,7,6 Frame Size=3 5 5 5 5 5 5 5 5 5 5 1 1 3 3 3 3 1 7 7 2 2 2 4 4 4 4 6 Page Fault: 8
- 6. Optimal Algorithm (i) Lowest Page Fault (ii)Replace the page that will not be used for the longest period of time Optimal Example Reference String is: 7,0,1,2,0,3,1,4,2,3 Frame Size=3 7 7 7 2 2 2 2 2 2 2 0 0 0 0 3 3 3 3 3 1 1 1 1 1 4 4 4 Page Fault :6