Scheduling Objectives in Process:

Schedulers typically attempt to achieve some combination of the following, goals. Note that, to some extent, these goals are contradictory:


Maximize CPU utilization (due to its relatively high cost).

Maximize utilization of other resources (disks, printers etc.).

Maximize throughput = number of jobs completed per unit time.

Minimize waiting time = total time a job spends waiting in the various queues for a resource to become available.

Minimize turnaround time = waiting time + computation time + I/O time.

Minimize response time (timesharing) = time from entry of a command until first output starts to appear.

Fairness: All comparable jobs should be treated equally.

Avoid indefinite postponement: It is normally avoided by using aging. In aging, the priority of a process, grows as it waits for a resource. The priority slowly becomes highest and it gets the resource.

Uniformity: The behavior of the system should be predictable.

Graceful degradation: The system, response deteriorates gradually rather than coming to a sudden virtual standstill in case of excessive loads.

Predictably: A given job should run in about the same amount of time and at about same cost regardless of system load.

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