Consider the process details given in the following table. A new pre-emptive…
2017
Consider the process details given in the following table.
A new pre-emptive scheduling algorithm is proposed, i.e., the Longest Remaining Time Next (LRTN), wherein ties are broken by giving priority to the process with the highest priority. Calculate the following:
i) Turnaround time for Process P2
ii) Response time for Process P3
- A.
(i) 20, (ii) 3
- B.
(i) 19, (ii) 3
- C.
(i) 19, (ii) 8
- D.
(i) 20, (ii) 7
Attempted by 82 students.
Show answer & explanation
Correct answer: A
Considering Priority: 1 > 2 > 3 > 4 (smaller number = higher priority), the book-style LRTN scheduling is:
Process BT AT Priority
P0 3 0 1
P1 9 2 4
P2 7 4 3
P3 6 3 2
Gantt Chart
0 2 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
| P0 | P1 | P2 | P1 | P3 | P2 | P1 | P3 | P2 | P1 | P3 | P2 | P1 | P3 | P2 | P1 | P3 | P2 | P1 | P0 | P3 | P2 | P1 |
Completion Time Table
Process AT BT CT TAT WT RT
P0 0 3 22 22 19 0
P1 2 9 25 23 14 0
P2 4 7 24 20 13 0
P3 3 6 23 20 14 3
Where
TAT = CT − AT
WT = TAT − BT
RT = First Start Time − Arrival Time
Required Answers
Turnaround Time of P2 = 24 − 4 = 20
Response Time of P3 = 6 − 3 = 3