OS Scheduler

Highest Response Ratio Next (HRRN)

HRRN chooses next process with the greatest ratio.

Accounts for age and short processes (better ratio).

Still requires knowing the service time.


  • R = response ratio,
  • w = time spent waiting for the processor, and
  • s = expected service time.

As with SRT and SPN, the expected service time must be estimated to use highest response ratio next (HRRN).