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

1. 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

2. 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 User Applications virtual machine interface Operating System physical machine interface Architecture

3. 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 User Application Operating System Architecture

4. 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

5. 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”

6. 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

7. 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

8. Operating System Interfaces

9. Software & hardware layer user User Program Executable Binary compiler Compiler Linker user mode OS interface System library kernel OS Operating System device drivers Hardware Architecture

10. 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.

11. System service call (monitor) Borland C library: Int printf(…) { // call SysOutputString, // provided by NT // system library, to // print on the screen SysOutputString(…); } C Programs: main() { // call printf, provided // by the C library, to // print on the screen printf(“Hello World!”); } NT library: Void SysOutputString(…) { // call NtOutputString, that in turn will call // video card driver to output strings to // the screen NtOutputString(…); }

12. System service call (disk) Borland C library: Int CreateFile(…) { // call NtCreateFile, // provided by NT to // create a file NtCreateFile(…); } C Programs: main() { // call CreateFile // by the C library, to // create a file on disk CreateFile(“a.txt”) } 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(…); }

13. System service calls (network) Borland C library: int createsocket(…) { … NtCreateSocket(…); } int send(…) { … NtSocketSend(…); } C Programs: main() { so = createsocket(); send(so, “text”); close(so); } NT library: Void NtCreateSocket(…) { … NtAfdCreateSocket(…); }

15. Virtual computer concept Virtual C++ Computer C++ compiler LISP interpreter Operating system Operating System Command interpreter FORTRAN compiler Macroinstruction interpreter Bare machine C compiler Assembler Virtual C Computer Java compiler …

16. 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

17. 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.

18. Embedded system architecture • 2-layered device • XBox • 3-layered device • Palm, PocketPC User Applications Embedded OS Application Hardware Hardware

19. General-purpose & embedded OS

20. Operating system concepts

21. 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.

22. 0 x vap0 vap1 page table 232 - 1 Virtual memory (address space) page 0 pp 0 page 1 pp 1 page 2 pp 2 x pp N paging file pp 212 physical memory (16MB) page 220 virtual address space (4GB)

23. 0 x vap0 vap1 page table 232 - 1 Virtual memory (address space) page 0 pp 0 page 1 pp 1 page 2 pp 2 pp N paging file pp 212 physical memory (16MB) page 220 virtual address space (4GB)

24. Memory manager pp 0 pp 1 pp 2 PT process VA pp N paging file pp 212 physical memory PT process VA

25. Memory manager pp 0 pp 1 pp 2 PT process VA pp N paging file pp 212 physical memory PT process VA

26. Memory manager (w/ constraint) x pp 0 pp 1 pp 2 PT process VA memory manager pp N paging file pp 212 physical memory PT process VA

27. 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)

28. Mode change: system call trap 1. System call traps to the kernel (kernel mode) 2. Kernel determines service routine required 3. Kernel services the call. 4. Control is returned to user program (user mode)

29. 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

30. scheduler ready running waiting Scheduler • A component in OS that decides which thread in the thread pool gets the CPU • Priority-based scheduler • Context switch new thread terminating threads signal events

31. 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

32. 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

33. Operating Systems and System Software Example: web server software

34. Web Server web cache Socket CM System Cache TCPIP FileSys network card User-mode web server architecture User Mode I/O module Kernel Mode

35. 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

36. User Code TWC.LIB I/O Module NTFS web cache SWC VA<->PA CM hit TCPIP - SWC web server architecture User Mode Kernel Mode miss System Cache network card +

37. SPECWEB’99 Performance *estimated scaling data

38. 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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