Process Scheduling Metrics

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.

 

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