Lecture9-intro-to-processes-part1

Lecture9-intro-to-pr - Announcements CS 3214 Computer Systems Systems Exercise 4 will be posted today Project 3 coming Lecture 9 Godmar Back CS

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1 CS 3214 Computer Systems Godmar Back Lecture 9 Announcements • Exercise 4 will be posted today • Project 3 coming CS 3214 Fall 2011 THREADS AND PROCESSES Part 1 CS 3214 Fall 2011 Processes • Def: An instance of a program in execution • OS provides each process with key abstractions – Logical control flow • 1 flow – single-threaded process • Multiple flows – multi-threaded process – Private address space – Abstracted resources: e.g., stdout/stdin file descriptors • These abstractions create the illusion that each process has access to its own – CPU (or CPUs for multi-threaded processes) – Memory – Devices: e.g., terminal CS 3214 Fall 2011 Context Switching • Historical motivation for processes was introduction of multi-programming: – Load multiple processes into memory, and switch to another process if current process is (momentarily) blocked This required protection and isolation between these – This required protection and isolation between these processes , implemented by a privileged kernel: dual- mode operation. • Time-sharing: switch to another process periodically to make sure all processes make equal progress • Switch between processes is called a context switch CS 3214 Fall 2011 Dual-Mode Operation • Two fundamental modes: – “kernel mode” – privileged
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This note was uploaded on 12/31/2011 for the course CS 3214 taught by Professor Staff during the Fall '11 term at Virginia Tech.

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Lecture9-intro-to-pr - Announcements CS 3214 Computer Systems Systems Exercise 4 will be posted today Project 3 coming Lecture 9 Godmar Back CS

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