Lecture29Full - COT 4600 Operating Systems Fall 2009 Click...

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Click to edit Master subtitle style 8/1/11 Lecture 29 COT 4600 Operating Systems Fall 2009 Dan C. Marinescu Office: HEC 304 Office hours: Tu-Th 3:00-4:00 PM
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Lecture 29 8/1/11 Lecture 29 – Tuesday November 30, 2010 ¨ Final exam – T December 9 4-6:50 PM n Last time: ¨ Stack replacement algorithms ¨ The clock algorithm n Today: ¨ Priority inversion ¨ Multi-level queue scheduling ¨ Comparison of scheduling algorithms ¨ Queuing n Next Time: ¨ Review of the class. 22
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Lecture 29 8/1/11 Priority scheduling n Each thread/process has a priority and the one with the highest ¨ Preemptive ¨ Non-preemptive n SJF is a priority scheduling where priority is the predicted next CPU burst time n Problem & Starvation – low priority threads/processes may never execute n Solution to starvation & Aging – as time progresses increase the priority of the thread/process n Priority my be computed dynamically 33
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Lecture 29 8/1/11 Priority inversion n A lower priority thread/process prevents a higher priority one from running. n T3 has the highest priority, T1 has the lowest priority; T1 and T3 share a lock. n T1 acquires the lock, then it is suspended when T3 starts. n Eventually T3 requests the lock and it is suspended waiting for T1 to release the lock. n
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This note was uploaded on 07/30/2011 for the course COP 4600 taught by Professor Montagne during the Spring '08 term at University of Central Florida.

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Lecture29Full - COT 4600 Operating Systems Fall 2009 Click...

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