lecture17-chapter09 - OperatingSystems Lecture17:...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
Operating Systems Lecture 17: Uniprocessor Scheduling Anda Iamnitchi anda@cse.usf.edu 1
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 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.
Background image of page 2
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?
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
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 workload 4
Background image of page 4
5 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
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
6 Terminology: Preemptive vs. 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. Non preemptive is used when suspending a process is impossible or very expensive: e.g., can’t “replace” a flight crew in middle of flight.
Background image of page 6
7 Scheduling Policies Batch systems:
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 8
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/18/2012 for the course COP 4600 taught by Professor Andaiamnitchi during the Fall '08 term at University of South Florida - Tampa.

Page1 / 28

lecture17-chapter09 - OperatingSystems Lecture17:...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online