Definition
Feedback Scheduling
Feedback scheduling is a dynamic priority-based strategy that penalises processes based on CPU usage. Processes using long continuous bursts are demoted to lower-priority queues.
Mechanism
Queue Structure
New processes enter the highest-priority queue (RQ0).
Time Slice Execution
A process runs for a specified time slice. If it uses the full slice without blocking, it is demoted to the next lower queue.
Promotion
To prevent starvation, processes in low-priority queues may be periodically promoted to higher queues.
Properties
Selection
Always pick from the highest-priority non-empty queue. Within a queue, FCFS or Round Robin may be used.
Preemptive
Higher-priority processes preempt lower-priority ones.
I/O Bias
Favour I/O-intensive and interactive processes, as they block frequently and stay in high-priority queues.
Dynamic Adaptation
Automatically adapts to process behaviour without requiring prior service time estimates.