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Chapter 1 (PART 2) Operating System Concepts

CS 414 Operating Systems. Chapter 1 (PART 2) Operating System Concepts. Department of Computer Science Southern Illinois University Edwardsville Summer, 2004 Dr. Hiroshi Fujinoki E-mail: hfujino@siue.edu. Chapter_One_2/001. Operating System Concepts.

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Chapter 1 (PART 2) Operating System Concepts

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  1. CS 414 Operating Systems Chapter 1 (PART 2) Operating System Concepts Department of Computer Science Southern Illinois University Edwardsville Summer, 2004 Dr. Hiroshi Fujinoki E-mail: hfujino@siue.edu Chapter_One_2/001

  2. Operating System Concepts This PPT presentation covers Section 1.5 of the textbook. CS 414 Operating Systems (1) Process (2) Deadlock avoidance in I/O resource management (3) Files and file descriptor (4) Special Files Chapter_One/002

  3. Subjects covered about “process” Q: What is “process”? “program” is an executable file stored in a disk program HDD Solutions Stored as a file CS 414 Operating Systems • What is “process”? • How is it different from “program”? • What we can do by “processes”? A: “Process” is a program in execution. Chapter_One/003

  4. Then how a “program” can become “process”? A program becomes a process Stored as a file CPU Load program Memory HDD CS 414 Operating Systems when one is loaded into the memory for execution by CPU Chapter_One/004

  5. Things needed for a program to be executed in memory PCB is a data structure for the CPU to keep track of each process CPU PCB-X PCB-A PCB-Z Address Space Program X Program Z HDD PCB = Process Control Block Process Memory CS 414 Operating Systems  Stack Memory  Program Code  Heap Memory Program Chapter_One/005

  6. Example of “program” and “process” • Program Static object, usually exists as an executable file • Process This is a program Program in execution This is a process (program in execution) CS 414 Operating Systems Chapter_One/006

  7. Intermediate summary of “process” Collection of assembly instructions CPU runs Stack data structure for sub-routine calls Other data structure (local/global variables) Questions  Where are PCBs located?  What information does PCB hold? CS 414 Operating Systems • It is a program in execution • A process consists of the contents in process address space and PCB • Process address space consists of:  Program Code  Stack Memory Space  Heap Memory Space Chapter_One/007

  8. Things needed for a program to be executed in memory CPU In the operating system PCB-X PCB-A PCB-Z Program X Program Z Program Y OS Memory CS 414 Operating Systems  Where are PCBs located? Chapter_One/008

  9. Deadlock avoidance in I/O resource management More than one process wait for resource for each other for forever HDD Example Process B Process A Deadlock wait Printer Assigned Assigned Resources wait CS 414 Operating Systems What is “deadlock”? • Assume that there are two processes • Each of the two processes requires printer and HDD at the same time • Without the printer and HDD, neither can finish its tasks (Circular-wait) Chapter_One/009

  10. Concept of files and file descriptor use close What is a file?  load Logical data storages in computer systems What is “file descriptor”? Logical identification for each file being used in a computer system. open read HDD user OS CS 414 Operating Systems file Chapter_One/010

  11. Concept of files and file descriptor (continued) Open “A.txt” Find/Access File Descriptor OS User File Allocation Table “A.txt” File Names Sector Locations Location on disk Load • Sectors • Track • Platters HDD File Names Y X B A CS 414 Operating Systems 1E23CD A.txt • Read (FD) • Write (FD) • Append (FD) Chapter_One/011

  12. Network Concept of Special Files Request Request Request (1) Special Files OS OS Internet Internet Users can I/O to many devices as if they were a file Response (4) HDD Ordinary File Can not be seen by human user HDD file user user Keyboard Modem Special Files printer CS 414 Operating Systems Chapter_One/012

  13. A concept in OS where a user can handle many I/O devices using the same interface (APIs) that is used for actual files. Special Files Read/Write Read-Only Write-Only CS 414 Operating Systems • When you open (reserve) a resource, OS gives you “descriptor” • Some special files are read-only and some others may be write-only - Printer - Keyboard - Disks - CRT Monitor - Mouse - Network - CD-ROM • CRT Monitor • (with touch-pen support) Chapter_One/013

  14. This PPT presentation covers Section 1.7 of the textbook.  Monolithic Structure  Layered Structure Windows uses these concepts Operating System Structure  VM (Virtual Machine)  Micro-Kernel CS 414 Operating Systems Chapter_One/014

  15. No structure in a collection of procedures Program OS Procedures Disk I/O Printer Spooler Monolithic Structure OS Process Mgmt. Memory Mgmt. user IPC KB I/O CS 414 Operating Systems • Operating systems are essentially a collection of procedures. Monolithic Structure OS (Any procedure or a user application can call any other procedure) • Big mess • But fast • (no overhead) Chapter_One/015

  16. Operating system as an executable program Printer Spooler KB I/O OS How is a Monolithic-Structured OS implemented? Concatenate into one source code file OS Procedures Compile IPC Memory Mgmt. Process Mgmt. Disk I/O Printer Spooler Disk I/O Source code modules Process Mgmt. Memory Mgmt. IPC KB I/O CS 414 Operating Systems Chapter_One/016

  17. External Commands Printer Spooler KB I/O “OS” in a broader definition OS How is a Monolithic-Structured OS implemented? IPC Memory Mgmt. exec (); System calls awk Process Mgmt. Disk I/O sort execute Program grep “OS Kernel” user CS 414 Operating Systems Operating system as an executable program Chapter_One/017

  18. Layers of priorities Process Management Memory Management I/O Management Layered Structure Operating Systems User Programs Process Communication CS 414 Operating Systems “Layers” Chapter_One/017-B

  19. user App1    Without VM App N Application programs Hardware With VM A virtual machine Virtual Machine (VM) Extra layer on top of hardware          OS2 OS1 OS3 Operating System Hardware Virtual Machine Support Windows 2000 UNIX MS-DOS CS 414 Operating Systems Chapter_One/018

  20.          For each application program, it looks like they are being executed by thededicated hardware Concept of VM          Hardware2 Hardware1 Hardware3 OS2 OS2 OS1 OS1 OS3 OS3 Hardware Virtual Machine Support CS 414 Operating Systems Chapter_One/019

  21. Implementation of of VM OS1 OS3 OS2 VM1 Process Manage Without VM Process X Process Y Process Z VM2 Process X Process Y Process M Process A Process B Process N Process Manage With VM VM3 Process Manage VMS OS VM Manage Process Manage Memory Memory CS 414 Operating Systems Chapter_One/020

  22. MS-DOS VM Win32 MS-DOS MS-DOS Windows-9x VM Hardware Virtual Machine Support CS 414 Operating Systems • All Win-32 applications are execute in Win-32 kernel • Each MS-DOS application will be executed within its VM Chapter_One/021

  23. A virtual computer where computer hardware is software-emulated by VMS (Virtual Machine Support) VM Summary of Virtual Machine (VM) - For flexibility Multiple operating systems (and its applications) at once - For robustness One VM crashes, others still survive CS 414 Operating Systems • Provide virtual dedicated machine (= hardware) to each OS (Q: What’s the difference from “multiple boot”?) (EG: Windows-NT) Chapter_One/022

  24. External Commands KB I/O Printer Spooler “OS” in a broader definition OS IPC Memory Mgmt. awk Process Mgmt. Micro-Kernel Architecture Disk I/O sort grep “OS Kernel” CS 414 Operating Systems Chapter_One/023

  25. Micro-Kernel Architecture (continued) External Commands Printer Spooler Printer Spooler KB I/O “OS” in a broader definition IPC Memory Mgmt. Memory Mgmt. awk Process Mgmt. Process Mgmt. Disk I/O sort OS grep “OS Kernel” CS 414 Operating Systems Chapter_One/024

  26. Micro-Kernel Architecture (continued) Kernel-Mode In ordinary OS (not Micro-Kernel OS), OS has to provide all the user services in Kernel-mode services User-Mode User Program System Call Operating System Computer Hardware OS Procedure (in the OS kernel) OS kernel tends to be huge CS 414 Operating Systems Chapter_One/025

  27. Micro-Kernel Architecture (continued) Kernel-Mode Server Make the OS kernel as small as possible Spooler User-Mode User Program Client Operating System Computer Hardware Micro-Kernel Architecture is based on Client-Server Model Operating System becomes a service broker CS 414 Operating Systems Micro-kernel Architecture Chapter_One/026

  28. Micro-Kernel Architecture (continued) A bug in OS can be fixed by replacing a module MS Windows uses micro-kernel architecture for this reason What is it good for? OS functions may be executed in user-mode CS 414 Operating Systems (1) Each OS function becomes a module (what we should do if “monolithic structure kernel”?) (2) Better robustness (a bug in a module will not crash the kernel) Chapter_One/027

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