MadeEasy Test Series: Operating System - Process Schedule

Question

In this question do we have to use non pre-emptive approach since it is said that the os schedules either when runnning process gets blocked I/O or when the running process finishes its cpu burst.And nothing is mentioned that the os pre-empts if a longer remaining time process completes its I/O and arrives for cpu execution while a shorter one is still executing. 

Comments

LRTF is pre-emptive in nature though "when the running process finishes its cpu burst" this line is unclear to me.

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The below statement is contradicting.

• We know that LRTF is pre-emptive. But, it is mentioned in the question that

The OS schedules a new process either when the running process gets blocked due to I/O or when it finishes its CPU burst.

Gantt chart:

$P_0$	$P_3$	$P_1$	$P_2$	$\text{stall}$	$P_0$	$\cdots$
$0 - 4$	$4 - 8$	$8 - 10$	$10 - 12$	$12 - 16$	$16 - 20$	$20 - \cdots$

 I got 20 as the answer.

Answer 1

If preemptive mode LRTF is used then

Is answer is 22 for p0 to complete??

Answer 2

Po will take 24 unit to complete

Comments

P0 takes 28units of time to complete.

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24

Answer 3

0   1     2     3     4     5     6     7     8      9     10   11   12          17  18   19   20   21  22    23   24   25   26  27   28   29

P0	P3	P0	P3	P0	P3	P0	P3	P1	P2	P1	P2		P1	P2	P0	P3	P0	P3	P0	P3	P0	P1	P2	P3

 

 

 

                        This is the gant chart that I am getting.

So according to this P0 is getting completed by 26 unit of time .

 

**Please say it is right or wrong.