Lecture 04 - Processor Management

Lecture 04 - Processor Management - Understanding Operating...

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Understanding Operating Systems Sixth Edition Chapter 4 Processor Management
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Understanding Operating Systems, Sixth Edition Learning Objectives After completing this chapter, you should be able to describe: The difference between job scheduling and process scheduling, and how they relate The advantages and disadvantages of process scheduling algorithms that are preemptive versus those that are nonpreemptive 2
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Understanding Operating Systems, Sixth Edition Learning Objectives (cont’d.) The goals of process scheduling policies in single- core CPUs Up to six different process scheduling algorithms The role of internal interrupts and the tasks performed by the interrupt handler This chapter is devoted to single processor systems. Those with multiple processors are discussed in Chapter 6. 3
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Understanding Operating Systems, Sixth Edition Overview In a simple system, one with a single user and one processor, the process is busy only when it is executing the user’s job When there are many users: A multiprogramming environment There are multiple processes competing to be run by a single CPU The processor must be allocated to each job in a fair and efficient manner. 4
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Understanding Operating Systems, Sixth Edition Overview Terms: Program (job) An inactive unit such as a file stored on a disk. Not a process. To an operating system, a program (job) is a unit of work submitted by the user. Process (task) An active entity that requires a set of resources, including: A processor Special registers A single instance of a program in execution. 5
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Understanding Operating Systems, Sixth Edition Overview (cont'd.) Thread A portion of a process that can run independently. The Processor (CPU) Central processing unit That part of the machine that performs calculations and executes the programs. Multiprogramming: Requires that the processor be allocated to each job or to each process for a period of time and deallocated at an appropriate moment. If the processor is deallocated during a program’s execution, it must be done to ensure that it can be restarted later as easily as possible. 6
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Understanding Operating Systems, Sixth Edition Overview (cont'd.) Interrupt Call for help Activates higher-priority program Context Switch Saving job processing information when interrupted (Page 108) A single processor can be shared by several jobs (processes) if: The OS has a scheduling policy, as well as a scheduling algorithm, to determine when to stop working on one job and proceed to another. 7
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Understanding Operating Systems, Sixth Edition About Multi-Core Technologies A dual-core, quad-core, or other multi-core CPU has more than one processor (core) on the computer chip. Multi-core engineering was driven by the problems
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Lecture 04 - Processor Management - Understanding Operating...

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