lec07-scheduling - Lecture 7: CPU Scheduling Chapter 5...

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Silberschatz, Galvin and Gagne ©2009 Operating System Concepts – 8 th Edition, Lecture 7: CPU Scheduling Chapter 5
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5.2 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts – 8 th Edition Schedulers ± Scheduler: a module in OS to execute scheduling decisions. ± Long-term scheduler (or job scheduler) – selects which processes should be brought into the ready queue ± Medium-term scheduler – selects which processes should be swapped in/out the memory ± Short-term scheduler (or CPU scheduler) – selects which process should be executed next and allocates CPU
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5.3 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts – 8 th Edition new ready running terminated blocked admitted interrupt/yield scheduled wait for event event occurrence exit, kill When is scheduling done?
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5.4 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts – 8 th Edition Big Picture 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.
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5.5 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts – 8 th Edition 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.
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5.6
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This note was uploaded on 02/17/2012 for the course COP 6611 taught by Professor Staff during the Spring '08 term at University of South Florida.

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lec07-scheduling - Lecture 7: CPU Scheduling Chapter 5...

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