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CS U480: Systems & Networks 1. Introduction Donghui Zhang Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 1 Syllabus Instructor: Donghui Zhang Class page linked from my home page: http://www.ccs.neu.edu/home/donghui Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 2 Your Background CSU380: Computer organization C/C++ programming System architecture: Processors, memory, I/O devices Processor architecture: ALU, instruction execution Assembly-level programming Familiarity with the C language and the standard C library Please consult with me if you are unsure your background is sufficient Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 3 Why Programming For CS: must. A pilot must know how to fly an airplane. For IS: also important. A project manager needs to have technical background. Bill Gates used to be a superb programmer. Guest speaker: Prof. Hafner. Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 4 Why C (and not Java) Talked with Mr. Feuer and Prof. Hafner. We provide guidance to what you should learn. (If you say “give us A without any exam or project”…) Most OS are implemented in C. Java hides many low-level details. This is a place to strengthen your C skills. Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 5 What is an Operating System? An operating system is a program that acts as an intermediary between a user of a computer and the computer hardware. Goals: Execute user programs and make solving user problems easier. Make the computer system convenient to use. Performance measures: Throughput: The total amount of work done over a period of time. Turnaround: The total time it takes to complete a job. Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 6 Concept Map Applications GUI Console OS CPU ALU Registers Memory Peripherals Disks Keyboard Mouse Display Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 7 Software Layers Application c = getc() Library read(…) Operating System kb_driver_read(…) Device driver read_device(…) A Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 8 Compilation vs. Execution During compilation, statements in higher-level languages are converted into machine code During execution, machine code is interpreted by a processor High-level language program Compiler Assembly language Assembler Machine code Libraries of Machine code Link editor Executable Shared Libraries Operating System Device Drivers Memory Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 9 Evolution of the OS In the beginning n Program stored in a hardware patch board or toggled in using switches Whirlwind at MIT PDP-1 from DEC Altair from MITS Program can access all of memory Program starts at location zero Loading programs by hand is slow and error-prone and painful, so . . . Program 0 Memory Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 10 Evolution of the OS: The Loader Create a very short program to load longer programs n Loader Toggle in bootstrap loader Primitive loader may load in program or a more complex loader to read from cards or tape Loading from cards is very slow, often took longer to load than to run, wasting (expensive) processor cycles, so . . . Program 0 Memory Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 11 Evolution of the OS: Batch Processing n Batch Loader Jobs are spooled on tape While one batch of jobs is running, card reader writes next batch of jobs on tape Jobs are read sequentially from tape into memory Tape is still relatively slow compared to processing Program 0 Memory Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 12 The Concept of a Job With the introduction of programming languages, a translator is needed to convert a program into machine code • When a program is stored on cards in the programming language, e.g., assembler or Fortran, it must be translated before it can be run • Example: To run a program written in Fortran 1. Load (machine code for) Fortran compiler 2. Run compiler: Compiler reads program, writes machine code 3. Load (machine code for) program 4. Run program Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 13 Evolution of the OS: Multiprogramming Load next program while previous program is running n Loader But now both programs can’t begin at address zero (in fact, starting address isn’t known in advance) Solutions? Program 2 Programs that perform lots of I/O waste (expensive) processor cycles Program 1 0 Memory Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 14 Evolution of the OS: Multitasking Share execution time among programs n When one program starts I/O, let the other run. What is needed to switch from one program to another? Loader + scheduler System data A program bug in one program Program 2 can overwrite another program, or the system programs and data, so . . . Program 1 0 Memory Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 15 Evolution of the OS: Protection Run programs in separate address spaces n System programs need to cross address spaces. System runs in privileged mode. Loader, scheduler, memory mgr System data The more programs in memory, Program 2 the less memory available for each program, so . . . Program 3 Program 1 0 Memory Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 16 Evolution of the OS: Virtual Memory Address space implemented in both main and secondary memory n Broken into pages A program’s address space is a set of pages. The address space for a program may be larger than main memory! Pages are swapped in and out of main memory as needed. Loader, scheduler, memory mgr, resource mgr 0 Memory Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum Disk 17 OS Diversity Great diversity of programmable hardware Nature of the OS depends on Super computers: simulation, scene generation, data mining Servers: database, web, video Personal: desktop, laptop Embedded: PDA, phone, media device Application mix Hardware capability Real-time requirements With the proliferation of embedded systems, most processors do not run a general purpose OS Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 18 OSes are complex programs developed over many years by many people They confront common problems that reappear in other contexts The problems have been formalized A variety of solutions have been proposed and implemented Choosing a solution requires evaluating tradeoffs of space, time, and complexity OSes are a rich source of well-designed sample programs We will study OSes by exploring common components Understand the motivation for each component Understand the tradeoffs for each implementation Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 19 Common System Components Process Management Main-Memory Management File System I/O System Network Management Let’s take a high-level tour of these components Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 20 Process Management A process is a program in execution To accomplish its task, a process needs certain resources: CPU time Memory Files I/O devices. The OS is responsible for the following activities in connection with processes: Process creation and deletion Process suspension and resumption Mechanisms for: Process synchronization Inter-process communication Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 21 From Program to Process Process Program High-level language program Compiler Assembly language Assembler Executable Machine code Libraries of Machine code Link editor Shared Libraries Operating System Device Drivers Memory Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 22 Memory Management Main memory is a large array of words Main memory is (usually) volatile Each word (or, often byte) has its own address Data in memory is shared by the CPU and I/O devices It loses its contents in the case of system failure. The OS is responsible for the following activities in connection with memory management: Keep track of which parts of memory are currently being used and by whom. Decide which processes to load when memory space becomes available. Allocate and deallocate memory space as needed. Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 23 Memory Management (cont.) n Loader, scheduler, memory mgr System data Program 2 Program 3 0 Program 1 Memory Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 24 Secondary-Storage Management Secondary storage is (usually) a large array of blocks Secondary storage is non-volatile and can be very large Each block has its own address Data is moved between main memory and secondary storage in units of blocks Disks are the most common in general purpose systems Memory cards and stick are common on portable devices The OS is responsible for the following activities in connection with secondary storage management: Free space management Storage allocation For disks, scheduling of block transfers Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 25 Secondary-Storage Management (cont.) n Loader, scheduler, memory mgr, resource mgr 0 Memory Disk Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 26 File Management A file is a collection of related information Files are stored within a file system From the view of most systems, a file is an array of bytes The OS is responsible for the following activities in connections with file management: File creation and deletion Directory creation and deletion Support of primitives for manipulating files and directories Mapping files onto secondary storage. File backup on stable (nonvolatile) storage media Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 27 I/O System Management Input/Output refers to the movement of data between main memory and peripheral devices Devices vary widely in their operation and behavior Devices are partitioned into classes to factor common behavior A device driver translates between general OS operations and device-specific commands I/O managements consists of A buffer-caching system A general device-driver interface Drivers for specific hardware devices Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 28 I/O System Management (cont.) Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 29 Network Management Networking allows distinct computer systems to exchange data Communication takes place using a protocol Networked computers vary widely in their degree of coupling: They may share a common OS and processes may be visible across systems They may share nothing except a communication port Networking allows users to access to non-local resources, allowing: Computation speed-up, through special purpose hardware or parallel processing Availability of data from other systems Enhanced reliability through redundancy Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 30 Network Management (cont.) Adapted from the slides prepared by Alan Feuer Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum 31