Scheduling Metrics: Scheduling metrics use to measure something, there are different metrics.

1. Arrival Time(AT): The time which the process became ready.

2. Burst Time(BT): Also called as service or execution or processing time is time spent executing in CPU.

3. Completion Time(CT): Also called as finish time is the time at the process completed its execution in CPU.

4. Turn Around Time(TAT): It is total time spent waiting for CPU and execution in CPU, i.e.,
   TAT = WT + BT = CT - AT
   Average TAT = ( Total TAT ) / (Total number of processes)
    

5. Waiting Time(WT): The time spent waiting for CPU.

   WT = TAT - BT
   Average WT = ( Total WT ) / (Total number of processes)
    

6. Response Time(RT): The time it takes to start responding to a request. It from first submission of the process until the first running.

   RT = ( Time of first response ) - ( Time of submission of request )
    

7. Throughput: The number of processes that are completed per unit time.

   Throughput = (Number of processes completed) / (Time unit)
    

8. Processor Utilization: The percentage of the time that CPU is busy, means not idle.

   Processor utilization = (Processor busy time) / (Processor busy time + Processor idle time)
    

Co-operative(non-preemptive) versus preemptive scheduling : There is two kind of CPU/Process scheduling algorithms:

1. Non preemptive scheduling: A running process can not be preempted till completed its execution in CPU,e.g., FIFO process scheduling, shortest job first(non-preemptive).

2. Preemptive scheduling: A running process can be preempted and CPU can be scheduled for another process, e.g., Round robin algorithm, Shortest remaining time first algorithm etc.