High response ratio priority scheduling algorithm

The Highest Response Ratio Priority Scheduling Algorithm (Highest Response Ratio Next) is an algorithm for allocating the response ratio of the CPU central controller. HRRN is a compromise algorithm between FCFS (first come first served algorithm) and SJF (short job priority algorithm). It takes into account both job waiting time and job running time, taking care of short jobs without making long job waiting time excessive. long, improving scheduling performance.

Definition (Recommended learning: PHP video tutorial)

High response ratio priority scheduling The basic idea of ​​the algorithm is to allocate the CPU to the process with the highest response ratio in the ready queue.

Basic idea

Short job priority scheduling algorithm Dynamic priority mechanism

Considers both the execution time of the job and the waiting time of the job, comprehensively Characteristics of the two algorithms: first come first served and shortest job first.

Principle

The high response ratio priority scheduling algorithm considers both the execution time of the job and the waiting time of the job, and combines first-come, first-served and shortest job priority. Characteristics of the algorithm.

The response ratio in this algorithm refers to the ratio of job waiting time to running time. The response ratio formula is defined as follows:

Response ratio = (waiting time required service time) / required service time, that is, RR =(w s)/s=1 w/s, so the response ratio must be greater than 1.

Advantages and Disadvantages

Balance between short jobs and priority, and long jobs will not be out of service for a long time

Response ratio calculation system overhead , increase system overhead

Applicable occasions

Batch processing system

Mainly used for job scheduling

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