ITFN 2601 Introduction to Operating Systems. Lecture 4 Scheduling. Agenda. Scheduling Batch Interactive Real-Time Threads. Scheduling: When. New Process is Created Parent Process Child Process Process Exits When a process blocks I/O Interrupt occurs Clock Interrupts Non-preemptive
ITFN 2601Introduction to Operating Systems
The amount of useful work accomplished per unit time. This depends, of course, on what constitutes “useful work.” One common measure of throughput is jobs/minute (or second, or hour, depending on the kind of job)
For each device, the utilization of a device is the fraction of time the device is busy. A good scheduling algorithm keeps all the devices (CPUs, disk drives, etc.) busy most of the time.
The length of time between when the job arrives in the system and when it finally finishes
The length of time between when a job arrives in the system and when it starts to produce output. For interactive jobs, response time might be more important than turnaround.
The amount of time the job is ready (runnable but not running). This is a better measure of scheduling quality than turnaround since the scheduler has no control of the mount of time the process spends computing or blocked waiting for I/O.