Definition
A non-preemptive scheduling technique that runs the process with the highest response ratio first, to ease starvation of long jobs
Visual IT Encyclopedia › Operating Systems › Process Management
Visual IT Encyclopedia › Operating Systems › Process Management
Definition
A non-preemptive scheduling technique that runs the process with the highest response ratio first, to ease starvation of long jobs
Setup: one CPU. P1–P4 are four programs (processes) to run. Arrival says at how many ms a process joined the line, and run time says how many ms it needs to run on the CPU to finish. Response ratios are shown rounded to two decimal places. (ms: a thousandth of a second)
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Highest Response-ratio Next (HRN) Scheduling
Each time a process finishes, the response ratio of every process in line is calculated, and the one with the highest ratio runs first. The response ratio is the waiting time plus the run time, divided by the run time. It is bigger when the run time is shorter and grows the longer a process waits, so even a long process eventually gets its turn. It is non-preemptive.
At a bank: customers with quick errands are called first, but customers who have waited a long time get extra points for it, so no one keeps getting pushed back.