Chapter10-OS7el - Operating Systems Internals and Design...

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Chapter 10 Multiprocessor  and Real-Time  Scheduling Seventh Edition By William Stallings Operating  Systems: Internals  and  Design  Principles
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Operating Systems: Operating Systems: Internals and Design Principles Internals and Design Principles Bear in mind, Sir Henry, one of the phrases in that  queer old legend which Dr. Mortimer has read to  us, and avoid the moor in those hours of darkness  when the powers of evil are exalted. —  THE HOUND OF THE BASKERVILLES,  Arthur Conan Doyle
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Synchronization Granularity  and Processes
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No explicit synchronization  among processes each represents a separate,  independent application or  job Typical use is in a time- sharing system
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Synchronization among processes, but at a very gross level Good for concurrent processes running on a multiprogrammed  uniprocessor can be supported on a multiprocessor with little or no change to user  software
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Single application can be effectively implemented as a collection of  threads within a single process programmer must explicitly specify the potential parallelism of an  application there needs to be a high degree of coordination and interaction among the  threads of an application, leading to a medium-grain level of  synchronization Because the various threads of an application interact so frequently,  scheduling decisions concerning one thread may affect the performance  of the entire application
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Represents a much more complex use of parallelism than is found in the  use of threads Is a specialized and fragmented area with many different approaches
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The approach taken will  depend on the degree of  granularity of  applications and the  number of processors  available
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A disadvantage of static assignment is that one processor can be idle,  with an empty queue, while another processor has a backlog to prevent this situation, a common queue can be used another option is dynamic load balancing
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Both dynamic and static methods require some  way of assigning a process to a processor Approaches: Master/Slave Peer
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Key kernel functions always run on a particular processor Master is responsible for scheduling Slave sends service request to the master Is simple and requires little enhancement to a uniprocessor  multiprogramming operating system Conflict resolution is simplified because one processor has control of all  memory and I/O resources
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Kernel can execute on any processor Each processor does self-scheduling from the pool of available processes
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Usually processes are not dedicated to processors
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