In computer science, a multilevel feedback queue is a scheduling algorithm. Scheduling algorithms are designed to have some process running at all times to keep the central processing unit (CPU) busy. [1] The multilevel feedback queue extends standard algorithms with the following design requirements:
The multilevel feedback queue was first developed by Fernando J. Corbató (1962). [2] For this accomplishment, the Association for Computing Machinery awarded Corbató the Turing Award. [3]
Whereas the multilevel queue algorithm keeps processes permanently assigned to their initial queue assignments, the multilevel feedback queue shifts processes between queues. [4] The shift is dependent upon the CPU bursts of prior time-slices. [5]
Multiple FIFO queues are used and the operation is as follows:
For scheduling, the scheduler always starts picking up processes from the head of the highest-level queue. Only if the highest-level queue has become empty will the scheduler take up a process from the next lower-level queue. The same policy is implemented for picking up in the subsequent lower-level queues. Meanwhile, if a process comes into any of the higher-level queues, it will preempt a process in the lower-level queue.
Also, a new process is always inserted at the tail of the top-level queue with the assumption that it will complete in a short amount of time. Long processes will automatically sink to lower-level queues based on their time consumption and interactivity level. In the multilevel feedback queue a process is given just one chance to complete at a given queue level before it is forced down to a lower-level queue.
In general, a multilevel feedback queue scheduler is defined by the following parameters: [6]
In computer science, a multilevel feedback queue is a scheduling algorithm. Scheduling algorithms are designed to have some process running at all times to keep the central processing unit (CPU) busy. [1] The multilevel feedback queue extends standard algorithms with the following design requirements:
The multilevel feedback queue was first developed by Fernando J. Corbató (1962). [2] For this accomplishment, the Association for Computing Machinery awarded Corbató the Turing Award. [3]
Whereas the multilevel queue algorithm keeps processes permanently assigned to their initial queue assignments, the multilevel feedback queue shifts processes between queues. [4] The shift is dependent upon the CPU bursts of prior time-slices. [5]
Multiple FIFO queues are used and the operation is as follows:
For scheduling, the scheduler always starts picking up processes from the head of the highest-level queue. Only if the highest-level queue has become empty will the scheduler take up a process from the next lower-level queue. The same policy is implemented for picking up in the subsequent lower-level queues. Meanwhile, if a process comes into any of the higher-level queues, it will preempt a process in the lower-level queue.
Also, a new process is always inserted at the tail of the top-level queue with the assumption that it will complete in a short amount of time. Long processes will automatically sink to lower-level queues based on their time consumption and interactivity level. In the multilevel feedback queue a process is given just one chance to complete at a given queue level before it is forced down to a lower-level queue.
In general, a multilevel feedback queue scheduler is defined by the following parameters: [6]