Process Management

Terminology

CPU Utilization:

• CPU Utilization is making the CPU is busy all the time, so that all the associated components of the system also utilized high. The maximum CPU utilization makes the system performance high.
• In another words, CPU utilization is the ratio of busy time of the processor to the total time passes for processes to finish.
• CPU utilisation may be calculated as –

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

Throughput :

• Throughput is the amount of work/task completed in a given interval of time/unit time.
• In another words, throughput is measured by means of the number of processes completed in a unit of time.
• The throughput can be calculated by using the formula:

Throughput = (No. of processes completed)/(Time unit)

Turnaround Time :

• Turnaround time is the time interval from the time of submission of a process to the time of its completion.
• It is the sum of the time spent waiting to get into memory, waiting in the ready queue, CPU time and I/O operations.

Turnaround Time = time(Process completed) – time(Process submitted)

Waiting Time :

• Waiting time is the time spent in the ready queue.
• As we know that, in multiprogramming operating system several jobs reside at a time in memory. CPU executes only one job among those at a time. The rest of jobs wait for the CPU. Thus, in multiprogramming environment, the waiting time may be expressed as turnaround time, less than the actual processing time.
• The waiting time may be calculated as :-

Waiting time = Turnaround Time – Processing Time.

Response Time :

• In time sharing system, Response time may be defined as interval from the time the last character of a command line of a program or transaction is entered to the time the last result appears on the terminal.
• In real time system, Response time may be defined as interval from the time an internal or external event is signalled to the time the first instruction of the respective service routine is executed.
• Response time may be calculated as –

Response time = time(first response) – time(submission of request)