Chap. 1) Introduction

Transcription

1 Chap. 1) Introduction 경희대학교컴퓨터공학과 조진성 Operating System

2 What is an Operating System? A program that acts as an intermediary between a user of a computer and the computer hardware Operating system goals: Execute user programs and make solving user problems easier Make the computer system convenient to use Use the computer hardware in an efficient manner Operating System 1

3 Abstract View of Computer System Components Operating System 2

4 Operating System Definitions Resource allocator manages and allocates resources Control program controls the execution of user programs and operations of I/O devices Kernel the one program running at all times (all else being application programs) Operating System 3

5 What is an OS? OS is a resource manager Abstraction Sharing Time multiplexing Space multiplexing Protection Fairness Performance Resources CPU Memory I/O devices OS provides the program execution environment Operating System 4

6 System Software Layers User applications Middlewares Software Development Environment (compilers, loaders, editors, utilities Command interpreter, libraries) Operating System (Kernel) Computer System Architecture Operating System 5

7 Computer-System Architecture Operating System 6

8 Computer-System Operation I/O devices and the CPU can execute concurrently Each device controller is in charge of a particular device type Each device controller has a local buffer CPU moves data from/to main memory to/from local buffers Cf) DMA (Direct Memory Access) I/O is from the device to local buffer of controller Device controller informs CPU that it has finished its operation by causing an interrupt Operating System 7

9 Modern PC Architecture Memory Controller Hub (MCH) I/O Controller Hub (ICH) Operating System 8

10 CPU Instruction Set Architecture RISC vs. CISC Intel, SPARC, MIPS, PowerPC, ARM, Alpha, Pipelining Fetch, Decode, Execute, Write Back, etc. Registers Program Counter (PC) Instruction Register (IR) Program Status Word (PSW) General-purpose registers Instruction-Level Parallelism(ILP) Superscalar vs. VLIW Simultaneous Multithreading Operating System 9

11 Mutual interaction The functionality of an OS is limited by architectural features Multiprocessing on DOS/8086? OS and Architecture The structure of an OS can be simplified by architectural support Interrupt, DMA, etc. Most proprietary OS s were developed with the certain architecture in mind Operating System 10

12 Storage Structure Main memory only large storage media that the CPU can access directly von Neumann architecture vs. Harvard architecture SRAM vs. DRAM DDR, QDR, RDRAM Secondary storage extension of main memory that provides large nonvolatile storage capacity Magnetic disks rigid metal or glass platters covered with magnetic recording material Disk surface is logically divided into tracks, which are subdivided into sectors The disk controller determines the logical interaction between the device and the computer Operating System 11

13 Moving-Head Disk Mechanism Operating System 12

14 A Modern Disk Drive IBM Deskstar 120GXP (120GB) Disks/Head: 3/6 Max. areal density: 29.7 Gbits/sq.inch Max. recording density: 524K BPI (bits/inch) Track density: 56.7K TPI (tracks/inch) Seek time: 8.5ms average Rotational latency: 7200rpm (8.3ms/rotation) Max. media transfer rate: 592 Mbits/sec Max. interface transfer rate: 100MB/sec Sustained data rate: 48 to 23 MB/sec SAMSUNG HD203WI (2TB) Seek time: 8.9ms Rotational latency: 5400rpm Max. media transfer rate: 300MB/sec Max. interface transfer rate: 135MB/sec Operating System 13

15 Storage Hierarchy Storage systems organized in hierarchy Speed Cost Volatility Caching copying information into faster storage system main memory can be viewed as a last cache for secondary storage Operating System 14

16 Storage-Device Hierarchy Operating System 15

17 Operating System 16 Memory Hierarchy

18 Caching Use of high-speed memory to hold recently-accessed data Requires a cache management policy Write-through vs. Write-back Caching introduces another level in storage hierarchy. This requires data that is simultaneously stored in more than one level to be consistent Cache coherency Operating System 17

19 Migration of A From Disk to Register Operating System 18

20 I/O Structure After I/O starts, control returns to user program only upon I/O completion Wait instruction idles the CPU until the next interrupt Wait loop (contention for memory access) At most one I/O request is outstanding at a time, no simultaneous I/O processing After I/O starts, control returns to user program without waiting for I/O completion System call request to the operating system to allow user to wait for I/O completion Device-status table contains entry for each I/O device indicating its type, address, and state Operating system indexes into I/O device table to determine device status and to modify table entry to include interrupt Operating System 19

21 I/O Control How does the kernel notice an I/O has finished? Polling Hardware interrupt Operating System 20

22 I/O Control (Cont d) Device interrupts CPU stops current operation, switches to kernel mode, and saves current PC and other state on kernel stack CPU fetches proper vector from vector table and branches to that address (to routine to handle interrupt) Interrupt routine examines device database and performs action required by interrupt Handler completes operation, restores saved (interrupt state) and returns to user mode (or calls scheduler to switch to another program) Operating System 21

23 Two I/O Methods From the perspective of applications Synchronous/ Blocking Asynchronous/ Non-blocking Operating System 22

24 Interrupts Generated by hardware devices Triggered by a signal in INTR or NMI pins (Pentium) Asynchronous Interrupts and Exceptions Exceptions Generated by software executing instructions INT instruction in IA32 Page fault, protection fault Synchronous Trap (expected) or fault (unexpected) Operating System 23

25 Data Transfer Modes in I/O Programmed I/O (PIO) By special I/O instructions Memory-mapped I/O DMA (Direct Memory Access) DMA Used for high-speed I/O devices able to transmit information at close to memory speeds Device controller transfers blocks of data from buffer storage directly to main memory without CPU intervention. Only an interrupt is generated per block Operating System 24

26 Hardware Protection I/O Protection Memory Protection CPU Protection Operating System 25

27 Dual-Mode Operation Sharing system resources requires operating system to ensure that an incorrect program cannot cause other programs to execute incorrectly Provide hardware support to differentiate between at least two modes of operations 1. User mode execution done on behalf of a user 2. Monitor mode (also kernel mode or system mode) execution done on behalf of operating system Operating System 26

28 Dual-Mode Operation (Cont d) Mode bit added to computer hardware to indicate the current mode: monitor (0) or user (1) When an interrupt or fault occurs hardware switches to monitor mode Interrupt/fault monitor user set user mode Privileged instructions can be issued only in monitor mode Operating System 27

29 I/O Protection All I/O instructions are privileged instructions Must ensure that a user program could never gain control of the computer in monitor mode (I.e., a user program that, as part of its execution, stores a new address in the interrupt vector) Operating System 28

30 Use of A System Call to Perform I/O Operating System 29

31 System Call Netscape: read( ) user mode kernel mode trap to kernel mode; save app state trap handler find read( ) handler in vector table restore app state, return to user mode, resume read( ) kernel routine Operating System 30

32 Memory Protection Must provide memory protection at least for the interrupt vector and the interrupt service routines In order to have memory protection, add two registers that determine the range of legal addresses a program may access: Base register holds the smallest legal physical memory address Limit register contains the size of the range Memory outside the defined range is protected Operating System 31

33 Use of A Base and Limit Register Operating System 32

34 Hardware Address Protection Operating System 33

35 MMU (Memory Management Unit) Memory management hardware provides more sophisticated memory protection mechanisms base and limit registers page table pointers, page protection, TLBs virtual memory segmentation Memory Protection Manipulation of memory management hardware are protected (privileged) operations Operating System 34

36 CPU Protection Timer interrupts computer after specified period to ensure operating system maintains control Timer is decremented every clock tick When timer reaches the value 0, an interrupt occurs Timer commonly used to implement time sharing Time also used to compute the current time Load-timer is a privileged instruction Operating System 35

37 How does the OS take control of CPU from the running programs? Use a hardware timer that generates a periodic interrupt The timer interrupt transfers control back to OS The OS preloads the timer with a time to interrupt. ( quantum ) 10ms for Linux Cf) time slice or time quantum The timer is privileged. Only the OS can load it Timers Operating System 36

38 Network Structure Local Area Networks (LAN) Relay, bridge, gateway, router, switch, hub Wide Area Networks (WAN) Operating System 37

39 Local Area Network Structure Operating System 38

40 Wide Area Network Structure Operating System 39

41 Computer Systems Mainframe systems Multiprogramming systems Time-sharing systems Desktop systems Parallel systems Distributed systems Clustered systems Real-time systems Embedded systems Handheld systems Operating System 40

42 Mainframe Systems Reduce setup time by batching similar jobs Automatic job sequencing automatically transfers control from one job to another. First rudimentary operating system Resident monitor initial control in monitor control transfers to job when job completes control transfers back to monitor Operating System 41

43 Memory Layout for a Simple Batch System Operating System 42

44 Multiprogrammed Batch Systems Several jobs are kept in main memory at the same time, and the CPU is multiplexed among them. Operating System 43

45 OS Features Needed for Multiprogramming I/O routine supplied by the system Memory management the system must allocate the memory to several jobs CPU scheduling the system must choose among several jobs ready to run Allocation of devices Operating System 44

46 Time-Sharing Systems Interactive Computing The CPU is multiplexed among several jobs that are kept in memory and on disk (the CPU is allocated to a job only if the job is in memory) A job swapped in and out of memory to the disk On-line communication between the user and the system is provided; when the operating system finishes the execution of one command, it seeks the next control statement from the user s keyboard On-line system must be available for users to access data and code Operating System 45

47 Terminology Batch, Multiprogramming, Time-sharing(or Multitasking) von Neumann architecture Job scheduling vs. CPU scheduling Job, Task, Process Concurrent, Simultaneous, Parallel Operating System 46

48 Desktop Systems Personal computers computer system dedicated to a single user I/O devices keyboards, mice, display screens, small printers User convenience and responsiveness Can adopt technology developed for larger operating system Individuals have sole use of computer and do not need advanced CPU utilization of protection features May run several different types of operating systems (Windows, MacOS, UNIX, Linux) Operating System 47

49 Parallel Systems Multiprocessor systems with more than one CPU in close communication Tightly coupled system processors share memory and a clock; communication usually takes place through the shared memory Advantages of parallel system: Increased throughput Economical Increased reliability graceful degradation fail-soft systems (fault-tolerant systems) Cf) Co-processor or controller Operating System 48

50 Parallel Systems (Cont d) Symmetric multiprocessing (SMP) Each processor runs and identical copy of the operating system Many processes can run at once without performance deterioration Most modern operating systems support SMP Asymmetric multiprocessing Each processor is assigned a specific task; master processor schedules and allocated work to slave processors More common in extremely large systems Operating System 49

51 Symmetric Multiprocessing Architecture Operating System 50

52 Distributed Systems Distribute the computation among several physical processors Loosely coupled system each processor has its own local memory; processors communicate with one another through various communications lines, such as high-speed buses or telephone lines Advantages of distributed systems Resources Sharing Computation speed up load sharing Reliability Communications Operating System 51

53 Distributed Systems (Cont d) Requires networking infrastructure Local area networks (LAN) or Wide area networks (WAN) May be either client-server or peer-to-peer systems Operating System 52

54 General Structure of Client-Server Operating System 53

55 Clustered Systems Clustering allows two or more systems to share storage Provides high reliability (or high availability) Asymmetric clustering: one server runs the application while other servers standby Symmetric clustering: all N hosts are running the application Cf) Grid Computing Cf) Distributed Lock Manager (DLM), Storage Area Network (SAN) Operating System 54

56 Real-Time Embedded Systems Often used as a control device in a dedicated application such as controlling scientific experiments, medical imaging systems, industrial control systems, and some display systems Well-defined fixed-time constraints Real-Time systems may be either hard or soft real-time Operating System 55

57 Real-Time Embedded Systems (Cont d) Hard real-time: Secondary storage limited or absent, data stored in short term memory, or readonly memory (ROM) Conflicts with time-sharing systems, not supported by general-purpose operating systems Soft real-time Limited utility in industrial control of robotics Useful in applications (multimedia, virtual reality) requiring advanced operatingsystem features Operating System 56

58 Handheld Systems Personal Digital Assistants (PDAs) Cellular telephones Issues: Limited memory Slow processors Small display screens Operating System 57

59 Computing Environments Traditional computing Client-Server computing Peer-to-Peer computing Web-based computing Operating System 58

60 Migration of Operating-System Concepts and Features Operating System 59

61 1st Generation ( ) Vacuum Tubes and Plugboards No OS No Programming Languages No Assembly Languages Operating System 60

62 2nd Generation ( ) Transistors and Mainframes Batch systems One job at a time Card readers, tape drives, line printers OS is always resident in memory and merely transfers a control. CPU is underutilized due to the bottleneck in I/O Operating System 61

63 3rd Generation ( ) Integrated Circuits (ICs) Architectural Advances Using ICs: better price/performance Disk drives On-line terminals The notion of Computer Architecture IBM System/360 family Operating System 62

64 3rd Generation ( ) Multiprogrammed Systems Increase CPU utilization OS features Job scheduling Memory management CPU scheduling Protection Spooling (Simultaneous Peripheral Operation On-Line) Operating System 63

65 3rd Generation ( ) Time-sharing Systems Improve response time OS features Swapping Virtual memory File system Sophisticated CPU scheduling Synchronization Interprocess communication Interactive shell More protection, Operating System 64

66 4th Generation (1980-) LSIs & VLSIs Architectural Advances Microprocessors: smaller and faster Storages: larger and faster Personal computers CPU work is offloaded to I/O devices Modern OS Features GUI (Graphical User Interface) Multimedia Internet & Web Networked / Distributed, etc. Operating System 65

67 OS History IBM OS/360: Multiprogramming A long time ago, in a galaxy far, far away, MIT CTSS (Compatible Time-Sharing System) MIT, Bell Labs, GE, MULTICS (MULTiplexed Information and Computing Service) And UNIX was born in 1969 Operating System 66

68 OS History: UNIX ( ) USG/USDL/ATTIS DSG/USO/USL Bell Labor atories Research Berkeley Software Distri butions 1969 Fi rst Edition 1973 Fifth Edition 1976 Sixth Edition 1977 PWB MER T CB UNIX 1BSD 1977 UNIX RT Seventh Editi on 2BSD 32V BSD BSD 1980 XENIX BSD Sys tem III 4.1aBSD System V XENIX 3 Eighth 4.1cBSD Edition 1984 Sys tem V SunOS 4.2BSD Release 2 2.8BSD 2.9BSD 1985 Figure 1.1 The UNIX system family tree, Operating System 67

69 OS History: UNIX ( ) Sys tem V Eighth 1985 Release 2 XENIX 3 SunOS Edition 4.2BSD 2.9BSD 1986 MACH 4.3BSD SunOS3 System V 1987 Release 3 Ninth 2.10BSD Chorus Edition XENIX MACH BSD-Tahoe System V 1989 Release 4 NeXT SunOS4 Tenth 2.11BSD Chorus Step Edition NET/1 V OSF/1 Plan 9 4.3BSD-Reno 1991 NET/2 386BSD 1992 Solaris NetBSD 0.8 Novell DEC UNIX FreeBSD 1.0 BSDI Linux UNIX Ware Solaris 2 4.4BSD BSD Lite SCO FreeBSD 2.0 BSDI 2.0 UNIX 4.4BSD Lite Figure 1.2 The UNIX system family tree, Operating System 68

70 OS History: UNIX (Current) Sun Solaris HP HP-UX IBM AIX Caldera (SCO) Unixware Compaq (Digital) Tru64 SGI Irix Linux, FreeBSD, NetBSD Apple Mac OS X, etc. Cf) POSIX Operating System 69

71 OS History: Windows & Linux MS-DOS Family Windows Family ME SE Windows for WorkGroup Family Windows NT Family K XP Linux Operating System 70

72 OS History: Windows & Linux (Cont d) ? Windows A.B.C A: Kernel version B: Major revision C: Minor revision Operating System 71

73 OS Classification (1) MS-DOS Windows 98 Windows NT Linux Multi-user X X O O Multi-task Multi-process X O O O Multi-processor X X O O Multi-thread X O O O Operating System 72

74 OS Classification (2) Monolithic Kernel Function calls Unixware, Solaris, AIX, HP-UX, Linux, etc. API Integrated Kernel Hardware Micro kernel Multiple servers Message passing Mach, Chorus, Linux mk, etc. API server server server Microkernel Hardware Operating System 73

75 Mainframe systems CTS, MULTICS, IBM MVS, VM Desktop systems DOS, Windows, MacOS, Unix/Linux Multiprocessor systems Cluster systems Distributed systems OS Classification (3) Amoeba(Vrije Univ.), Locus(UCLA), Grapevine(Xerox), V(Stanford), Eden(U. of Washington), Chorus/Nucleus(Inria) Embedded systems Vertex, psos, VxWorks, OSE, Windows-CE, Embedded Linux Company-proprietary OS (Cisco, Qualcomm, Palm, Cellvic) Real-time systems Real-Time Linux, Spring(U. of Massachusetts), HARTS(U. of Michigan), MARUTI(U. of Maryland) Operating System 74

76 Operating system An intermediary software between users and computer hardware Summary Goals of operating system Use the computer hardware in efficient manners Convenient programming & use through encapsulation of complexity of H/Ws Maximization of performance of computer hardware resources Operating System 75

77 Computer system architecture & Operation CPU, Memory, I/O devices Instructions Arithmetic instructions: add, subtract, Logical instructions: and, or, not, Control flow instructions: goto, if, call, return, Data instructions: load, store, move, input, output, Interrupt DMA Summary (Cont d) When I/O events occur, I/O devices trigger an interrupt CPU saves its operation and runs the corresponding interrupt service routine (ISR) Transfers blocks of data from I/O devices to main memory without CPU intervention Storage hierarchy Register / Cache / Main memory / Secondary storage / Tertiary storage Operating System 76

78 Computer system architecture & Operation (Cont d) System call Summary (Cont d) An interface to the service made available by operating system When a user process calls a system call, controls are transferred from the user process to operating system user mode vs. kernel mode Protection I/O protection: Dual-mode operation Memory protection: MMU (Memory Management Unit) CPU protection: Timer interrupt History of computer systems Mainframe systems or batch systems Multiprogramming systems Time-sharing systems Desktop systems Parallel / Distributed / Clustered / Cloud systems Real-time / Embedded / Handheld systems Operating System 77