LM.Lecture3 - Distributed Operating Systems CS551 Colorado...

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Unformatted text preview: Distributed Operating Systems CS551 Colorado State University at Lockheed-Martin Lecture 3 -- Spring 2001 7 February 2001 CS-551, Lecture 3 2 CS551: Lecture 3 ■ Topics – Real Time Systems (and networks) – Interprocess Communication (IPC) ■ message passing ■ pipes ■ sockets ■ remote procedure call (RPC) – Memory Management 7 February 2001 CS-551, Lecture 3 3 Real-time systems ■ Real-time systems : – systems where “the operating system must ensure that certain actions are taken within specified time constraints” Chow & Johnson, Distributed Operating Systems & Algorithms , Addison-Wesley (1997). – systems that “interact with the external world in a way that involves time … When the answer is produced is as important as which answer is produced.” Tanenbaum, Distributed Operating Systems , Prentice-Hall (1995). 7 February 2001 CS-551, Lecture 3 4 Real-time system examples ■ Examples of real-time systems – automobile control systems – stock trading systems – computerized air traffic control systems – medical intensive care units – robots – space vehicle computers (space & ground) – any system that requires bounded response time 7 February 2001 CS-551, Lecture 3 5 Soft real-time systems ■ Soft real-time systems – “missing an occasional deadline is all right” Tanenbaum, Distributed Operating Systems , Prentice-Hall (1995). – “have deadlines but are judged to be in working order as long as they do not miss too many deadlines” Chow & Johnson, Distributed Operating Systems & Algorithms , Addison-Wesley (1997). – Example: multimedia system 7 February 2001 CS-551, Lecture 3 6 Hard real-time systems ■ Hard real-time systems – “only judged to be correct if every task is guaranteed to meet its deadline” Chow & Johnson, Distributed Operating Systems & Algorithms , Addison-Wesley (1997). – “a single missed deadline … is unacceptable, as this might lead to loss of life or an environ- mental catastrophe” Tanenbaum, Distributed Operating Systems , Prentice-Hall (1995). 7 February 2001 CS-551, Lecture 3 7 Hard/Soft real-time systems ■ “A job should be completed before its deadline to be of use (in soft real-time systems) or to avert disaster (in hard real- time systems). The major issue in the design of real-time operating systems is the scheduling of jobs in such a way that a maximum number of jobs satisfy their deadlines.” Singhal & Shivaratri, Advanced Concepts in Operating Systems , McGraw-Hill (1994). 7 February 2001 CS-551, Lecture 3 8 Firm real-time systems ■ Firm real-time systems – “similar to a soft real-time system, but tasks that have missed their deadlines are discarded” Tanenbaum, Distributed Operating Systems , Prentice-Hall (1995)....
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This note was uploaded on 06/12/2011 for the course CS 551 taught by Professor Staff during the Summer '08 term at Colorado State.

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LM.Lecture3 - Distributed Operating Systems CS551 Colorado...

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