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Modern Operating Systems

Modern Operating Systems. B.Ramamurthy Chapter 2, Section 2.4. Topics. New developments and influences Microkernel Architecture Multithreading Symmetric Multiprocessing Distributed Systems Object-oriented design Windows NT architecture Traditional Unix Kernel Summary.

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Modern Operating Systems

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  1. Modern Operating Systems B.Ramamurthy Chapter 2, Section 2.4

  2. Topics • New developments and influences • Microkernel Architecture • Multithreading • Symmetric Multiprocessing • Distributed Systems • Object-oriented design • Windows NT architecture • Traditional Unix Kernel • Summary

  3. New Developments • Hardware : increased machine speed, high speed network attachments, increased size of memory storage, lower cost • Application : multimedia, internet, intranet, Web computing, client/server computing • Software : Object Oriented design and programming

  4. Influences on OS • Wide range of design approaches: 1. Microkernel architecture 2. Multithreading 3. Symmetric multiprocessing 4. Distributed Operating Systems 5. Object-oriented design

  5. Microkernel Architecture • Essential services such as address space management, interprocess communications, and basic scheduling are done by the kernel. • For the rest of the services special servers are designed separately. • Flexibility in design and for support of distributed system. • Highly suited for customizing services for various environments. • Example: Mach system, CTRX realtime kernel for 8051

  6. Multithreading • A thread is dispatchable unit of work. • Many threads can execute the code in the same process space. • Code for multithread should be re-entrant : What is reentracy? • Also known as lightweight process since the overhead in thread switching and control is much less compared to process control switching. • Example: Windows NT , Solaris

  7. Symmetric Multiprocessing (SMP) • Many of today’s systems have multiple microprocessors • The architecture is known as SMP if the processors share the same main memory and IO space and can be used interchangeably. (do the same functions) • For performance and reliability (availability, maintainability, scalability, fault-tolerance). • Ex: Windows NT and Solaris

  8. Distributed Systems • A distributed system is a collection of independent computers that appear to the users of the system as a single computer. • In this age of geographically distributed data sources and clients this model works very well. • Question is : network connected, network-transparent, network-centric model, or clusters?

  9. Object Oriented Design • Lends discipline to the process of extending small kernels. • Customization of the operating system without disrupting system integrity. • Forms the basis for remote location of services, mobility, accountability, security etc. • Supports Client-server paradigm of computing. • Example: Windows NT

  10. Features of Windows NT ( Fig.2.13) • User mode and Kernel mode : Separation of user and kernel functions. • Modified microkernel architecture. • Windows NT Executive: Executive services • HAL : Hardware Abstraction Layer : abstract unberlying machine (alpha, intel, etc.) • System services (user interface)

  11. Features of Traditional Unix kernel • User level kernel level • System call subsystem • User programs may access kernel thru’ libraries or directly thru’ system calls: Which one preferred and why? • File Subsystem, Process Control subsystem • Study Fig 2.17 (modern unix kernel functions)

  12. Summary • Major OS Topics include: Process management, File management, scheduling, IO management, concurrency, memory management, security. • Keep up with recent developments. • Distribution of services and resources is an very critical topic.

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