CPU Scheduling Algorithm Practice

Question	Answer
1. Assume that the following jobs are to be executed on a single processor system ------------------------------------------------------ Job-Id \| Burst Time -------------------------------------------------------- p \| 4 q \| 1 r \| 8 s \| 1 t \| 2 --------------------------------------------------------- The jobs are assumed to have arrived at time 0 and in the order p, q, r, s, t. Calculate the departure time (completion time) for job p if scheduling is round robin with time slice 1.	Ans: 11 Image: c7d8aaad-01e0-441d-bb89-9a8b29cfa744 (image/png)
2. Consider the following set of processes, with the arrival times and the CPU burst times given in milliseconds. ----------------------------------------------------------- Process \| Arrival-Time \| Burst-Time ----------------------------------------------------------- P1 \| 0 \| 5 P2 \| 1 \| 3 P3 \| 2 \| 3 P4 \| 4 \| 1 ----------------------------------------------------------- What is the average turnaround time for these processes with the preemptive shortest remaining processing time first (SROT) algorithm?	Image: c49c541b-8f6e-4d58-9c03-05bca301d900 (image/png)
3. An operating system uses Shortest Remaining Time first (SRT) process scheduling algorithm. Consider the arrival times and execution times for the following processes: ----------------------------------------------------------- Process\| Execution time\| Arrival time ----------------------------------------------------------- P1 \| 20 \| 0 P2 \| 25 \| 15 P3 \| 10 \| 30 P4 \| 15 \| 45 ----------------------------------------------------------- What is the total waiting time for process P2?	Image: 5d3b1cc3-c054-42b7-986c-0530f947b7e7 (image/png)
4. Consider the following table of arrival time and burst time for three processes P0, P1 and P2. ----------------------------------------------------------- Process \| Arrival time \| Burst Time ----------------------------------------------------------- P0 \| 0 ms \| 9 ms P1 \| 1 ms \| 4 ms P2 \| 2 ms \| 9 ms ----------------------------------------------------------- The pre-emptive shortest job first scheduling algorithm is used. Scheduling is carried out only at arrival or completion of processes. What is the average waiting time for the three processes?	Image: eb3b2dba-589a-440a-ada1-10fbbe5fccfa (image/png)
5. First-Come, First-Served (FCFS) Scheduling ----------------------------------------------------------- Process \| Burst Time ----------------------------------------------------------- P1 \| 24 P2 \| 3 P3 \| 3 ----------------------------------------------------------- Suppose that the processes arrive in the order: P1 , P2 , P3 Calculate average waiting time.	Image: 3f6acda4-66a4-4cde-9bea-79dc5b2f2776 (image/png)
6. Shortest-Job-First (SJF) (Non-Preemptive) ----------------------------------------------------------- Process \| Arrival Time \| Burst Time ----------------------------------------------------------- P1 \| 0 \| 7 P2 \| 2 \| 4 P3 \| 4 \| 1 P4 \| 5 \| 4 ----------------------------------------------------------- Calculate average waiting time.	Image: 4853b508-5198-4bd5-880d-df12244b2f44 (image/png)
7. Preemptive SJF ----------------------------------------------------------- Process \| Arrival Time \| Burst Time ----------------------------------------------------------- P1 \| 0 \| 7 P2 \| 2 \| 4 P3 \| 4 \| 1 P4 \| 5 \| 4 ----------------------------------------------------------- Calculate average waiting time.	Image: fe58f042-12c1-487e-a4d1-93acca374693 (image/png)
8. Say we have the process arrival time chart given below. ----------------------------------------------------------- Process\| Arrival time\| Burst Time ----------------------------------------------------------- P1 \| 0 \|16 P2 \| 0 \|10 P3 \| 6 \| 4 P4 \| 7 \| 6 P5 \| 8 \|10 ----------------------------------------------------------- Draw a Gantt chart to illustrate how these processes would be scheduled using Round Robin (RR).Assume that the quantum is set to 5 time units.	Image: 6a9421f6-9aff-4d48-96c3-d4766c6e734a (image/png)

1. Assume that the following jobs are to be executed on a single processor system ------------------------------------------------------ Job-Id | Burst Time -------------------------------------------------------- p | 4 q | 1 r | 8 s | 1 t | 2 --------------------------------------------------------- The jobs are assumed to have arrived at time 0 and in the order p, q, r, s, t. Calculate the departure time (completion time) for job p if scheduling is round robin with time slice 1.

Ans: 11

Image: c7d8aaad-01e0-441d-bb89-9a8b29cfa744 (image/png)

2. Consider the following set of processes, with the arrival times and the CPU burst times given in milliseconds. ----------------------------------------------------------- Process | Arrival-Time | Burst-Time ----------------------------------------------------------- P1 | 0 | 5 P2 | 1 | 3 P3 | 2 | 3 P4 | 4 | 1 ----------------------------------------------------------- What is the average turnaround time for these processes with the preemptive shortest remaining processing time first (SROT) algorithm?

Image: c49c541b-8f6e-4d58-9c03-05bca301d900 (image/png)

3. An operating system uses Shortest Remaining Time first (SRT) process scheduling algorithm. Consider the arrival times and execution times for the following processes: ----------------------------------------------------------- Process| Execution time| Arrival time ----------------------------------------------------------- P1 | 20 | 0 P2 | 25 | 15 P3 | 10 | 30 P4 | 15 | 45 ----------------------------------------------------------- What is the total waiting time for process P2?

Image: 5d3b1cc3-c054-42b7-986c-0530f947b7e7 (image/png)

4. Consider the following table of arrival time and burst time for three processes P0, P1 and P2. ----------------------------------------------------------- Process | Arrival time | Burst Time ----------------------------------------------------------- P0 | 0 ms | 9 ms P1 | 1 ms | 4 ms P2 | 2 ms | 9 ms ----------------------------------------------------------- The pre-emptive shortest job first scheduling algorithm is used. Scheduling is carried out only at arrival or completion of processes. What is the average waiting time for the three processes?

Image: eb3b2dba-589a-440a-ada1-10fbbe5fccfa (image/png)

5. First-Come, First-Served (FCFS) Scheduling ----------------------------------------------------------- Process | Burst Time ----------------------------------------------------------- P1 | 24 P2 | 3 P3 | 3 ----------------------------------------------------------- Suppose that the processes arrive in the order: P1 , P2 , P3 Calculate average waiting time.

Image: 3f6acda4-66a4-4cde-9bea-79dc5b2f2776 (image/png)

6. Shortest-Job-First (SJF) (Non-Preemptive) ----------------------------------------------------------- Process | Arrival Time | Burst Time ----------------------------------------------------------- P1 | 0 | 7 P2 | 2 | 4 P3 | 4 | 1 P4 | 5 | 4 ----------------------------------------------------------- Calculate average waiting time.

Image: 4853b508-5198-4bd5-880d-df12244b2f44 (image/png)

7. Preemptive SJF ----------------------------------------------------------- Process | Arrival Time | Burst Time ----------------------------------------------------------- P1 | 0 | 7 P2 | 2 | 4 P3 | 4 | 1 P4 | 5 | 4 ----------------------------------------------------------- Calculate average waiting time.

Image: fe58f042-12c1-487e-a4d1-93acca374693 (image/png)

8. Say we have the process arrival time chart given below. ----------------------------------------------------------- Process| Arrival time| Burst Time ----------------------------------------------------------- P1 | 0 |16 P2 | 0 |10 P3 | 6 | 4 P4 | 7 | 6 P5 | 8 |10 ----------------------------------------------------------- Draw a Gantt chart to illustrate how these processes would be scheduled using Round Robin (RR).Assume that the quantum is set to 5 time units.

Image: 6a9421f6-9aff-4d48-96c3-d4766c6e734a (image/png)

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CPU Scheduling Algorithm Practice

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