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EE110300 電機資訊工程實習

Lecture 3 個人電腦系統 II ---- Operating Systems

資訊工程系 黃泰一 教授

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What is an operating system?Definition An operating system is the “permanent”

software that controls/abstracts hardware User applications can thus be simpler and

device-independent

physical machine interface

User Applications

Operating System

Architecture

virtual machine interface

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What is an operating system?Definition (con’t) Manages resources and processes to support

different user applications Provides Applications Programming

Interface (API) for user applications

User Application

Operating System

Architecture

User Application

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Modern operating systems

x86 platform– Linux– Windows

Mac platform – Mac OS Sun Solaris & Unix (Sun workstations) IBM AIX (mainframes) Embedded systems (special-purpose OS)

– Palm, PocketPC, etc– Xbox, etc

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Linus Torvalds

1991, Finland, Linux Project 1992, Linux Kernel 0.02

– Bash v1.08– GCC v1.40

1997, Moves to Transmeta 1998, Linux Kernel v2.2 2001, Linux Kernel v2.4 Pronunciation: “Linn-ucks”

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Windows 2000 & XP

1989: 10 developers left DEC VMS team and joined Microsoft Windows NT 1.0

1996: Windows NT 4.0 1999: Windows 2000 2001: Windows XP 2002: Microsoft .Net Server

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Linux vs. Windows NT

Linux is kernel only, free and open source Windows is full-loaded OS and pricy Linux requires minimum HW, Windows not Web server

– (Win2K + SWC ) beats (Linux + TUX) File server & printer server

– Windows supports a wider range of HW– Linux has more stable drivers

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Operating System Interfaces

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Software & hardware layer

User Program Executable Binary

Compiler Linker

System library

Architecture

user

compiler

OS interface

OS

Hardware

device driversOperating System

kernel

user mode

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Device Driver

Device driver 的唯一目的就是要將所有的硬體隱藏 .

他應該是整套軟體中唯一能和硬體溝通的窗口 .

他能直接讀取或寫入特定裝置控制及狀態暫存器 , 如果裝置發生中斷 ,那 ISR 也要整合到裝置驅動程式 .

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System service call (monitor)C Programs:

main() {

// call printf, provided

// by the C library, to

// print on the screen

printf(“Hello World!”);

}

Borland C library:Int printf(…) {// call SysOutputString,// provided by NT // system library, to// print on the screenSysOutputString(…);}

NT library:Void SysOutputString(…) {// call NtOutputString, that in turn will call // video card driver to output strings to // the screenNtOutputString(…);}

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System service call (disk)C Programs:main() {// call CreateFile // by the C library, to// create a file on diskCreateFile(“a.txt”)}

Borland C library:Int CreateFile(…) {// call NtCreateFile,// provided by NT to// create a fileNtCreateFile(…);}

NT library:Void NtCreateFile(…) { // call NtInternalCreateFile, that in turn will // call the file system driver and the disk // driver to create a file on a disk NtInternalCreateFile(…);}

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System service calls (network)

C Programs:main() {so = createsocket();send(so, “text”);close(so);}

Borland C library:int createsocket(…) { … NtCreateSocket(…);}

int send(…) { … NtSocketSend(…);}

NT library:

Void NtCreateSocket(…) { … NtAfdCreateSocket(…);}

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Virtual computer concept

C++ compiler

FORTRAN compiler

C compiler

Java compiler …

Assembler

OperatingSystem

Commandinterpreter

LISP interpreter

Operating system

Macroinstruction interpreter

Bare machine

Virtual CComputer

Virtual C++Computer

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Importance of operating system

System API are the only interface between user applications and hardware– API are designed for general-purpose, not

performance driven (e.g. network applications)

OS code cannot allow any bug– Any break (e.g. invalid access) causes reboot

The owner of OS technology controls the software industry

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What is Embedded System?

是電腦軟體與硬體的綜合體 , 亦可涵蓋機械或其他附屬裝置 ; 整個綜合體設計的目的 , 在於滿足某種特殊功能 .

例如 : PDA, 遊樂器 , 衛星導航系統 , 流程管理器 等 .

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Embedded system architecture

3-layered device– Palm, PocketPC

User Applications

Embedded OS

Hardware

2-layered device– XBox

Hardware

Application

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General-purpose & embedded OS

General-purpose Embedded OS

Examples Linux, Windows WinCE, Palm OS

Hardware General-purpose Special device

OS code size Large Small

Stability req. Strong Weak

Develop. cost Huge Medium

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Operating system concepts

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Process & Thread

How do different applications run on the same machine at the same time without interfering each other?– Protection between processes– Protection between a process and the OS

Process: an execution of a program, consisting of a virtual address space, one or more threads, and some OS states.

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Virtual memory (address space)

0

232 - 1

virtual address space (4GB)

page 0

page 1

page 2

page 220

vap0

vap1

x

page table

physical memory (16MB)

pp 0

pp 1

pp 2

pp N

paging filepp 212

x

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Virtual memory (address space)

0

232 - 1

virtual address space (4GB)

page 0

page 1

page 2

page 220

vap0

vap1

x

page table

physical memory (16MB)

pp 0

pp 1

pp 2

pp N

paging filepp 212

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Memory manager

physical memory

pp 0

pp 1

pp 2

pp N

paging filepp 212

process VA

process VA

PT

PT

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Memory manager

physical memory

pp 0

pp 1

pp 2

pp N

paging filepp 212

process VA

process VA

PT

PT

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Memory manager (w/ constraint)

physical memory

pp 0

pp 1

pp 2

pp N

paging filepp 212

process VA

process VA

PT

PT

x

memory manager

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Protectiondual mode operation Can application modify its own page table?

If it could, could get access to all physical memory.

Dual Mode– Kernel/protected model: no restriction, can

touch any physical memory page– User mode: where you program runs, can only

touch part of the virtual address space Applications can enter the kernel mode

through systems calls (traps)

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Mode change: system call trap

1. System call traps to the kernel (kernel mode)2. Kernel determines service routine required3. Kernel services the call.4. Control is returned to user program (user mode)

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Thread

A process starts with one thread (main thread), and can initialize more threads by CreateThread() calls

A thread represents an execution stream of instructions and its CPU register context

A thread is the unit used in the scheduler Kill a process kill its all threads

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Scheduler A component in OS that decides which

thread in the thread pool gets the CPU Priority-based scheduler Context switch

new thread

schedulerready

runningwaiting terminatingthreads

signalevents

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Synchronization

All threads in the same process share all global data

Synchronization among these threads is necessary to maintain data integrity

Resource lock is commonly used to guarantee thread mutual exclusive– abuse of such locks decreases scalability– ignorance of such locks decreases stability

Deadlock issues

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File Systems

A hard disk is just a raw media storage A hard disk device driver allows OS to

communicate with the hardware But, it is the responsibility of the OS to organize

disk sectors/tracks for storing files– such component is called the file system

E.g. A hard disk that stores NTFS information cannot be read with the FAT32 driver– example: paper with Moses code

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Operating Systems and System Software

Example: web server software

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User-mode web server architectureWeb Server

CM

web cache

network card

TCPIP

User Mode

Kernel ModeI/O module

SocketSystem Cache

FileSys

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User-mode web server commons

User-mode application architecture– e.g. Microsoft Internet Information Server (IIS),

Netscape Enterprise Server, Apache HTTP Server, etc.

Dependent on generally system API Stand-alone web content cache limited by

virtual address space Time-to-live cache replacement algorithm Memory-less dynamic code execution

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SWC web server architecture

User Mode

Kernel Mode

TCPIP -NTFS

CM

web cache

network card +

System Cache SWCmiss

I/O Module

TWC.LIBUser Code

VA<->PA

hit

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SPECWEB’99 Performance

15122694

4800*5600*

1638

4409

6371

12309

14400

5600

9016

2198222719

0

4,000

8,000

12,000

16,000

20,000

24,000

Requests/Sec

UP 4P 8P

Linux + ZeusW2K + IIS 5.0IBM-AIX + ZeusLinux + TUX W2K + SWC

*estimated scaling data

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Kernel vs. user-based web server

Increase peak capacity by five times Web cache size be limited by physical

memory size Web cache be shared by both static &

dynamic web requests Remove I/O overhead and Socket creation Fast TCPIP data transmission

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Summary

# persons

many

few

skills

easy

difficult

control

small

large

reward

low

high

Apps

EOS

A.D. 1492 Columbus discovers America--- The new and free land is on your grip!!