lecture17-chapter09 - Operating Systems Operating Systems...

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Unformatted text preview: Operating Systems Operating Systems Lecture 17: Lecture 17: Uniprocessor Scheduling Uniprocessor Scheduling Anda Iamnitchi anda@cse.usf.edu 1 2 CPU and I/O Bursts CPU and I/O Bursts Long CPU burst Short CPU burst Waiting for I/O CPU not needed. Process goes to blocked/waiting state. Interrupt: back from I/O operation, ready to use the CPU. 3 Scheduling absolutely required when: A process exists A process becomes blocked (on I/O, etc) Scheduling may be required when: New process created I/O interrupt Clock interrupt new ready running terminated blocked admitted interrupt/yield scheduled wait for event event occurrence exit, kill When is short-term scheduling done? Short-Term Scheduling Criteria Short-Term Scheduling Criteria User-oriented scheduling criterion: Response Time: elapsed time between the submission of a request until there is output System-oriented scheduling criterion: Effective and efficient utilization of the processor Performance-related Response time and throughput Non-performance related Predictability: variances as a function of 4 5 Scheduling Performance Metrics Scheduling Performance Metrics All systems: Fairness Policy enforcement Balance Batch Systems: Throughput Turnaround time CPU utilization Interactive Systems: Response time Proportionality Real-time Systems: Meeting deadlines Predictability Waiting time : turnaround time minus solo execution time 6 Terminology: Preemptive vs. Terminology: Preemptive vs. non-Preemptive non-Preemptive Preemptive: A Process can be suspended and resumed Non-preemptive: A process runs until it voluntarily gives up the CPU (waiting on I/O or terminate). Most modern OSs use preemptive CPU scheduling, implemented via timer interrupts....
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lecture17-chapter09 - Operating Systems Operating Systems...

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