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Scheduling Algorithm Evaluation Criteria

User-oriented evaluation criteria

These criteria focus on user experience and mainly examine the impact of scheduling algorithms on users: From this picture, we can see the following evaluation criteria for scheduling algorithms: Of course, MathJax can be used to express formulas. The following is a detailed display of the formula:

  1. Short average turnaround time:
  2. Turnaround time is defined as the time interval from when a job is submitted to the system to when the job is completed, calculated as completion time minus arrival time.
  3. The formula for average turnaround time is:
\[ T = \frac{1}{n} \left[ \sum_{i=1}^{n} T_i \right] \]

Where \( T_i \) represents the turnaround time of the \( i \)th job, and \( n \) is the total number of jobs.

  1. Weighted turnaround time:
  2. Weighted turnaround time is defined as the ratio of the turnaround time \( T \) of a job to the time \( T_S \) (running time) that the system provides services for it.
  3. The formula for average weighted turnaround time is:
\[ W = \frac{1}{n} \left[ \sum_{i=1}^{n} \frac{T_i}{T_{Si}} \right] \]

Where \( T_{Si} \) is the running time of the \( i \)th job.

These criteria are used to evaluate the pros and cons of scheduling algorithms. Shorter average turnaround time and lower average weighted turnaround time can improve the system's responsiveness and user satisfaction.

  • Deadline guarantee: In real-time systems, the deadline refers to the maximum delay time that users can tolerate. The pros and cons of scheduling algorithms are usually reflected in whether the start deadline and the completion deadline can be met. Especially in real-time systems, whether tasks can be completed on time is crucial.

  • Priority criteria: In many types of systems, especially batch, time-sharing, and real-time systems, some tasks may be more urgent than others. Scheduling algorithms need to ensure that high-priority tasks are processed first.

System-oriented evaluation criteria

These criteria focus more on the performance and resource utilization within the system: - System throughput: the number of processes that the system can complete per unit time. The higher the throughput, the stronger the system's processing power.

  • Processor utilization: the ratio of the CPU's effective working time to the total running time. The scheduling algorithm needs to ensure efficient use of the CPU and avoid too much idle time.

  • Balanced use of various resources: Reasonable scheduling of resource allocation to avoid excessive use of some resources and idleness of other resources. The system's resource utilization should be balanced to avoid bottleneck problems.

Scheduling algorithm implementation criteria

These criteria focus on the actual implementation of the scheduling algorithm: - Effectiveness: whether the scheduling algorithm can achieve its design goals as expected, that is, improve system performance and meet user needs.

  • Ease of implementation: whether the algorithm is easy to implement, maintain and adjust. Some complex algorithms may have excellent performance, but may be too complex to implement and difficult to maintain.