Highest Response Ratio Next

The non- preemptive scheduling method Highest Response Ratio Next ( HRRN ) always assigns the processor to the process with the highest response ratio. This ratio is calculated as follows:

Note: For the times to be used are to be estimated values ​​, since usually no sufficiently reliable indication of future behavior is possible.

The scheduler will be only be active if the last allocated process is terminated or blocked (eg, I / O operations ). This scheduling algorithm preferred processes with low computational time because of this the response ratio with increasing waiting time increases more quickly. It also prevents livelocks for long processes, which distinguishes him from Shortest - Remaining- Time ( SRT) or Shortest -Job- First ( SJF ).

The formula can be further simplified to:

Since the values ​​are compared only by the scheduler with each other, could be the one eliminated as well.

Swell

  • William Stallings: Operating Systems: principles and implementation. 4th Edition, Prentice- Hall, Munich 2002, ISBN 3-8273-7030-2.
  • Operating system theory
Scheduling (computing)
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