multiprocessor scheduling (5)

multiprocessor scheduling (5) - COP 4600 Summer 2011...

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COP 4600: Intro To OS (Multiprocessor Scheduling) Page 1 © Dr. Mark Llewellyn COP 4600 – Summer 2011 Introduction To Operating Systems Multiprocessor Scheduling Department of Electrical Engineering and Computer Science Computer Science Division University of Central Florida Instructor : Dr. Mark Llewellyn [email protected] HEC 236, 407-823-2790 http://www.cs.ucf.edu/courses/cop4600/sum2011
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COP 4600: Intro To OS (Multiprocessor Scheduling) Page 2 © Dr. Mark Llewellyn Scheduling In A Multiprocessor System When a computer system contains more than one processor, several new issues are introduced into the design of scheduling protocols. Load sharing becomes an issue for the scheduler. As with uniprocessor scheduling protocols, there is no one best protocol that will suffice for all situations. For the most part we will only be concerned with homogeneous systems, in which the processors are identical in terms of their functionality.
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COP 4600: Intro To OS (Multiprocessor Scheduling) Page 3 © Dr. Mark Llewellyn Classifications of Multiprocessor Systems Loosely coupled, distributed multiprocessors, or clusters Fairly autonomous systems. Each processor has its own memory and I/O channels Functionally specialized processors Typically, specialized processors are controlled by a master general- purpose processor and provide services to it. An example would be an I/O processor. Tightly coupled multiprocessing Consists of a set of processors that share a common main memory and are under the integrated control of an operating system. We’ll be most concerned with this group.
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COP 4600: Intro To OS (Multiprocessor Scheduling) Page 4 © Dr. Mark Llewellyn Multiprocessor Systems Interconnection Network P P P Memory disk Memory Memory disk disk Shared Nothing (Loosely Coupled) P P P Interconnection Network Global Shared Memory disk disk disk Shared Memory (Tightly Coupled) Memory Memory Memory P P P Interconnection Network disk disk disk Shared Disk
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COP 4600: Intro To OS (Multiprocessor Scheduling) Page 5 © Dr. Mark Llewellyn Multiprocessor Systems The basic problem with the shared-memory and shared-disk architectures is interference . As more CPUs are added, existing CPUs are slowed down because of the increased contention for memory accesses and network bandwidth. It has been shown that: An average of 1% slowdown per additional CPU limits the maximum speed-up to a factor of 37. Adding additional CPUs actually slows down the system. A system with 1000 CPUs is only 4% as effective as a single CPU. These observations motivated the development of the shared-nothing architectures for parallel systems. These systems are particularly useful for database systems.
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COP 4600: Intro To OS (Multiprocessor Scheduling) Page 6 © Dr. Mark Llewellyn Multiprocessor Systems Linear speed-up occurs when the time required by an operation decreases in proportion to the increase in the number of CPUs and disks. Linear
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This note was uploaded on 10/03/2011 for the course COP 4600 taught by Professor Montagne during the Summer '08 term at University of Central Florida.

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multiprocessor scheduling (5) - COP 4600 Summer 2011...

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