Multi-level feedback queue scheduler Q consists of 3 linear queues, i.e., Q1, Q2, and Q3.
- Q1 is round robin with time quantum 8,
- Q2 is round robin with time quantum 16, and
- Q3 follows FIFO
- The process cannot be executed in the lower queue if there are any jobs in all higher queues. For example, Q1 has 5 processes, Q2 has 1 process, and Q3 has 1 process. Then, first the process in Q1 should be executed (and completed), and then a process in Q2 is executed. Finally, Q3 will get CPU resource.
- A new process enters queue Q1 which is served RR8.
- When it gains CPU, a process receives 8 milliseconds.
- If it does not finished in 8 milliseconds, the process is moved to queue Q2.
- At Q2 process is again served RR16 and receives 16 additional milliseconds.
- If it still does not complete, it is preempted and moved to queue Q3.
- At Q3 process is executed by first come first serve.
- If it still does not complete, it is processed at Q2 until completed.
OUTPUT:
The remaining time of processes in each queue level, total waiting time and total turnaround time are displayed.
