Definition
Service Time Estimation
Service time estimation predicts the next CPU burst length for a process, required for SPN, SRT, and HRRN.
Uses exponential averaging of past bursts:
: Actual length of most recent burst : Previous estimate : Weighting factor ( )
- Close to 1: Responds quickly to recent changes
- Close to 0: Stable, ignores transient spikes
Properties
Fairness
Overestimating a burst may unfairly delay a short process.
Starvation Prevention
Underestimating may allow CPU-intensive processes to monopolise the processor when shorter bursts are prioritised.