File - Mr Rizal Arbain

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TUTORIAL 1
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
1.
2.
3.
4.
5.
6.
7.
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.
FIFO PROCEDURE
Example form Textbook;
Figure 3.8
1.
PAGE FRAMES = 2
2.
JOB PAGES = 4 (A,B,C,D)
3.
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
1
2
Page Request
A
B
Page fault/Interrupt
*
*
A
A
B
Page Frame 1
Page Frame 2
3
4
5
6
7
8
9
10
11
C
A
B
D
B
A
C
D
*
*
*
*
*
*
*
A
C
C
B
B
B
A
A
D
B
B
A
A
D
D
D
C
C
A
Answer/Explanation FIFO
COMPLETED ANSWER
1.
2.
3.
4.
5.
6.
7.
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
1
2
Page Request
A
B
Page fault/Interrupt
*
*
A
A
3
A
4
5
6
7
8
9
10
11
C
A
B
D
B
A
C
D
*
*
*
*
*
A
D
D
A
A
D
B
B
B
B
C
C
*
Page Frame 1
A
A
A
Page Frame 2
B
B
C
C
Answer/Explanation LRU