Scheduling criteria is also called as scheduling methodology. Key to multiprogramming is scheduling. Different CPU scheduling algorithm have different properties .The criteria used for comparing these algorithms include the following:
Keep the CPU as busy as possible. It range from 0 to 100%. In practice, it range from 40 to 90%.
Throughput is the rate at which processes are completed per unit of time.
This is the how long a process takes to execute a process. It is calculated as the time gap between the submission of a process and its completion.
Waiting time is the sum of the time periods spent in waiting in the ready queue.
Response time is the time it takes to start responding from submission time. It is calculated as the amount of time it takes from when a request was submitted until the first response is produced.
Each process should have a fair share of CPU.
Scheduling Algorithm Goals
- Fairness:- Fair share of CPU to every process
- Policy Enforcement: Stated policy is implemented properly
- Balance: Keeping all resources equally busy
- Throughput:- Maximize jobs per unit time
- Turnaround Time:- Minimization of time between submission and termination
- CPU Utilization:- Keep CPU busy all the time
- Response Time:- Quick response to request
- Proportionality:- Meet user’s expectation
Real Time System:
- Meeting Deadlines:- Avoiding losing data
- Predictability:- Avoid quality degradation