# File - Mr Rizal Arbain

## FIFO vs LRU

First-in first-out

(FIFO) policy: a page replacement policy that removes from main memory the pages that were brought in first.

*KEY = Identify what are FIRST PAGE REQUEST for in and out?

Least recently used

(LRU) policy: a page-replacement policy that removes from main memory the pages that show the least amount of recent activity.

*KEY=Identify what are the LATEST PAGE to standby for out?

### DEFINITION

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Identify how much PAGE FRAMES are available.

Identify how much JOB PAGES.

Identify job to process (PAGE REQUESTED).

Identify PAGE swapped IN to and OUT of memory (from Page Frames) Marks each interrupt with an asterisk.

Count the number of page interrupts.

Compute the FAILURE rate and the SUCCESS rate.

### Example form Textbook; Figure 3.8

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PAGE FRAMES = 2 JOB PAGES = 4 (A,B,C,D) Arrangement PAGE REQUESTED = A, B, A, C, A, B, D, B, A, C, D So, Total number Page Requested are 11.

QUESTION : Using the FIFO page removal algorithm, does a page trace analysis indicating page faults with asterisks (*). Then compute the failure and success ratios.

### Identify Requirement

Time

Page Request Page fault/Interrupt Page Frame 1 1 A * A 2 B * A 3 A A 4 C * C 5 A * C 6 B * B 7 D * B 8 B B 9 A * A 10 C * A 11 D * D B B B A A D D D C C Page Frame 2

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Identify how much PAGE FRAMES are available.

Identify how much JOB PAGES.

Identify job to process (PAGE REQUESTED).

Identify LEAST RECENTLY USED PAGE of memory (standby to out) Marks each interrupt with an asterisk.

Count the number of page interrupts.

Compute the FAILURE rate and the SUCCESS rate.

LRU chooses the page that has not been used for the longest period of time .

### LRU PROCEDURE

Time

Page Request Page fault/Interrupt 1 A * 2 B * 3 A 4 C * 5 A 6 B * 7 D * 8 B 9 A * 10 C * 11 D * Page Frame 1 A A A A A A D D A A D Page Frame 2 B B C C B B B B C