This is a short presentation of a BCA subject OPERATING SYSTEM of ch.- Memory Management on topic "page replacement algorithm".. Thank you

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