1. (CPU
SCHEDULING)
SAREENA WANGPITAK

2. (CPU SCHEDULING)
♦
CPU
OS
♦
(context switching)

3. (CPU SCHEDULING)


1


4. 


I/O


5. 


I/O

6. CPU

7. (CPU SCHEDULER)
“
” (Short-term Scheduler)

8. (PREEMPTIVE SCHEDULING)
1.
(run)
(wait)
/
2.
(run)
3.
(ready)

9. 3
1.
PCB
2.
3.
PCB

10. (SCHEDULING ALGORITHMS)
Dispatcher
1.
2.
3.
Context
user mode

11. (SHORT-TERM SCHEDULER)
OS
(Short-term scheduler)
OS

12. (SHORT-TERM SCHEDULER)
1.
(FCFS :
First-Come First-Served)
2.
(SJF :
Short-Job-First Scheduling)
3.
(Priority Scheduling)
4.
(RR : Round-
Robin Scheduling)

13. (FCFS : FIRST-COME FIRST-SERVED)



FIFO queue)

PCB
PCB

14. (FCFS : FIRST-COME FIRST-SERVED)…
3
(A,B,C)
CPU
cpu
A
B
C
1
2
3
15
0
0+15=15
1
15
15+1=16
10
16
16+10=26
=(11+1+11)/3 = 7.67

15. (FCFS : FIRST-COME FIRST-SERVED)…
A,B,C
A
B
15
C
16
26
A
=0
B
= 15
C
= 16

16. (FCFS : FIRST-COME FIRST-SERVED)…
FCFS
B
1
A
=(15+16)/3=10.33
B
1/16*100 = 6%
100-6 = 94%
16

17. (SHORTEST-JOB FIRST SCHEDULING : SJF )

18. (SHORTEST-JOB FIRST SCHEDULING : SJF )…
P1, P2, P3
P4
P1
P2
P3
P4
6
8
7
3

19. (SHORTEST-JOB FIRST SCHEDULING : SJF )…
Gantt Chart




P1
P2
P3
P4

20. (PRIORIT Y SCHEDULING)
Priority)




21. (PRIORIT Y SCHEDULING)…
P1
P2
P3
P4
P5
6
8
7
3
5
3
1
3
4
2

22. (PRIORIT Y SCHEDULING)…
P2, P5, P1, P3, P4
P2, P5, P1, P3, P4
Aging

23. (RR : ROUND-ROBIN SCHEDULING)
(Ready Queue)
timer
1

24. (RR : ROUND-ROBIN SCHEDULING)…
RR
CPU
3
(A,B,C)
1
cpu
A
B
C
1
2
3
15
1
10
11
1
11
= (11+1+11)/3 =
15+11=26
1+1=2
10+11=21

25. (RR : ROUND-ROBIN SCHEDULING)…
A B C A C A C A C A C A C A C A C A C A C A A A A A
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

26. (RR : ROUND-ROBIN SCHEDULING)
RR
B
CPU
A
CPU

27. 3
= 10
A
B
C
D
E
FCFS,SJF
10
29
3
7
12
RR

28. A
0
B
10
C
20 23
D
E
30
B
40
E
50 52
B
61
RR
A=0
B=10
C=20
D=10+10+3=23
E=10+10+3+7=30
(0+10+20+23+30)/5
=16.6
A=0+10=10
B=10+29=39
C=20+3=23
D=23+7=30
E=30+12=42
10+39+23+30+42/5

29. MULTILEVEL QUEUE SCHEDULING)
interactive)
batch)

30. MULTILEVEL QUEUE SCHEDULING)…

31. MULTILEVEL QUEUE SCHEDULING)…
-

32. MULTILEVEL QUEUE SCHEDULING)…
system processes)
interactive processes)
interactive edition



processes)


batch processes)
student processes)

33. MULTILEVEL QUEUE SCHEDULING)…