Advance Operating System Lecture 1 PDF

Advance Operating System Edited by Dr. Akram Alhammadi Chapter 1: Introduction What Operating Systems Do Computer-System Organization Computer-System Architecture Operating-Syst...

Advance Operating System Edited by Dr. Akram Alhammadi Chapter 1: Introduction What Operating Systems Do Computer-System Organization Computer-System Architecture Operating-System Structure Operating-System Operations Process Management Memory Management Storage Management Protection and Security Operating System Concepts – 9th Edition 1.2 Silberschatz, Galvin and Gagne ©2013  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 Concepts – 9th Edition 1.3 Silberschatz, Galvin and Gagne ©2013 Computer System Structure Computer system can be divided into four components:  Hardware – provides basic computing resources  CPU, memory, I/O devices  Operating system  Controls and coordinates use of hardware among various applications and users  Application programs – define the ways in which the system resources are used to solve the computing problems of the users  Word processors, compilers, web browsers, database systems, video games  Users  People, machines, other computers Operating System Concepts – 9th Edition 1.4 Silberschatz, Galvin and Gagne ©2013  Four Components of a Computer System Operating System Concepts – 9th Edition 1.5 Silberschatz, Galvin and Gagne ©2013 What Operating Systems Do Depends on the point of view Users want convenience, ease of use and good performance  Don’t care about resource utilization But shared computer such as mainframe or minicomputer must keep all users happy (care about resource utilization) Users of dedicate systems such as workstations have dedicated resources but frequently use shared resources from servers(compromise between individual usability and resource utilization) Handheld computers are resource poor, optimized for usability and battery life Some computers have little or no user interface, such as embedded computers in devices and automobiles Operating System Concepts – 9th Edition 1.6 Silberschatz, Galvin and Gagne ©2013  Operating System Definition OS is a resource allocator  Manages all resources  Decides between conflicting requests for efficient and fair resource use OS is a control program  Controls execution of programs to prevent errors and improper use of the computer Operating System Concepts – 9th Edition 1.7 Silberschatz, Galvin and Gagne ©2013 Operating System Definition (Cont.) No universally accepted definition “The one program running at all times on the computer” is the kernel. Everything else is either  a system program (ships with the operating system) , or  an application program. Operating System Concepts – 9th Edition 1.8 Silberschatz, Galvin and Gagne ©2013  Computer Startup bootstrap program is loaded at power-up or reboot  Typically stored in ROM or EPROM, generally known as firmware  Initializes all aspects of system  Loads operating system kernel and starts execution Operating System Concepts – 9th Edition 1.9 Silberschatz, Galvin and Gagne ©2013 Computer System Organization Computer-system operation  One or more CPUs, device controllers connect through common bus providing access to shared memory  Concurrent execution of CPUs and devices competing for memory cycles Operating System Concepts – 9th Edition 1.10 Silberschatz, Galvin and Gagne ©2013  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 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 Concepts – 9th Edition 1.11 Silberschatz, Galvin and Gagne ©2013 Common Functions of Interrupts Interrupt transfers control to the interrupt service routine generally, through the interrupt vector, which contains the addresses of all the service routines Interrupt architecture must save the address of the interrupted instruction A trap or exception is a software-generated interrupt caused either by an error or a user request An operating system is interrupt driven Operating System Concepts – 9th Edition 1.12 Silberschatz, Galvin and Gagne ©2013  Interrupt Handling The operating system preserves the state of the CPU by storing registers and the program counter Determines which type of interrupt has occurred:  Polling (based on time of interrupt)  vectored interrupt system (Based on priority) Separate segments of code determine what action should be taken for each type of interrupt Operating System Concepts – 9th Edition 1.13 Silberschatz, Galvin and Gagne ©2013 Storage Definitions and Notation Review The basic unit of computer storage is the bit. A bit can contain one of two values, 0 and 1. All other storage in a computer is based on collections of bits. Given enough bits, it is amazing how many things a computer can represent: numbers, letters, images, movies, sounds, documents, and programs, to name a few. A byte is 8 bits, and on most computers it is the smallest convenient chunk of storage. For example, most computers don’t have an instruction to move a bit but do have one to move a byte. A less common term is word, which is a given computer architecture’s native unit of data. A word is made up of one or more bytes. For example, a computer that has 64-bit registers and 64- bit memory addressing typically has 64-bit (8-byte) words. A computer executes many operations in its native word size rather than a byte at a time. Computer storage, along with most computer throughput, is generally measured and manipulated in bytes and collections of bytes. A kilobyte, or KB, is 1,024 bytes a megabyte, or MB, is 1,0242 bytes a gigabyte, or GB, is 1,0243 bytes a terabyte, or TB, is 1,0244 bytes a petabyte, or PB, is 1,0245 bytes Computer manufacturers often round off these numbers and say that a megabyte is 1 million bytes and a gigabyte is 1 billion bytes. Networking measurements are an exception to this general rule; they are given in bits (because networks move data a bit at a time). Operating System Concepts – 9th Edition 1.14 Silberschatz, Galvin and Gagne ©2013  Storage Structure Main memory – only large storage media that the CPU can access directly  Random access  Typically volatile Secondary storage – extension of main memory that provides large nonvolatile storage capacity Hard 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 Solid-state disks – faster than hard disks, nonvolatile  Various technologies  Becoming more popular Operating System Concepts – 9th Edition 1.15 Silberschatz, Galvin and Gagne ©2013 Storage Hierarchy Storage systems organized in hierarchy  Speed  Cost  Volatility Caching – copying information into faster storage system; main memory can be viewed as a cache for secondary storage Device Driver for each device controller to manage I/O  Provides uniform interface between controller and kernel Operating System Concepts – 9th Edition 1.16 Silberschatz, Galvin and Gagne ©2013  Storage-Device Hierarchy Operating System Concepts – 9th Edition 1.17 Silberschatz, Galvin and Gagne ©2013 Caching Important principle, performed at many levels in a computer (in hardware, operating system, software) Information in use copied from slower to faster storage temporarily Faster storage (cache) checked first to determine if information is there  If it is, information used directly from the cache (fast)  If not, data copied to cache and used there Cache smaller than storage being cached  Cache size and replacement policy Operating System Concepts – 9th Edition 1.18 Silberschatz, Galvin and Gagne ©2013  Direct Memory Access Structure 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 Operating System Concepts – 9th Edition 1.19 Silberschatz, Galvin and Gagne ©2013 How a Modern Computer Works Operating System Concepts – 9th Edition 1.20 Silberschatz, Galvin and Gagne ©2013  Computer-System Architecture Most systems use a single general-purpose processor  Most systems have special-purpose processors as well Multiprocessors systems growing in use and importance  Also known as parallel systems, tightly-coupled systems  Multiprocessor systems have three main advantages: 1. Increased throughput 2. Economy of scale 3. Increased reliability – graceful degradation or fault tolerance  Two types: 1. Asymmetric Multiprocessing – each processor is assigned a special task. 2. Symmetric Multiprocessing – each processor performs all tasks Operating System Concepts – 9th Edition 1.21 Silberschatz, Galvin and Gagne ©2013 Symmetric Multiprocessing Architecture Operating System Concepts – 9th Edition 1.22 Silberschatz, Galvin and Gagne ©2013  A Dual-Core Design Multi-chip and multicore Systems containing all chips  Chassis containing multiple separate systems Operating System Concepts – 9th Edition 1.23 Silberschatz, Galvin and Gagne ©2013 Clustered Systems Like multiprocessor systems, but multiple systems working together  Usually sharing storage via a storage-area network (SAN)  Provides a high-availability service which survives failures  Asymmetric clustering has one machine in hot-standby mode  Symmetric clustering has multiple nodes running applications, monitoring each other  Some clusters are for high-performance computing (HPC)  Applications must be written to use parallelization  Some have distributed lock manager (DLM) to avoid conflicting operations Operating System Concepts – 9th Edition 1.24 Silberschatz, Galvin and Gagne ©2013  Clustered Systems Operating System Concepts – 9th Edition 1.25 Silberschatz, Galvin and Gagne ©2013 Operating System Structure Multiprogramming (Batch system) needed for efficiency  Single user cannot keep CPU and I/O devices busy at all times  Multiprogramming organizes jobs (code and data) so CPU always has one to execute  A subset of total jobs in system is kept in memory  One job selected and run via job scheduling  When it has to wait (for I/O for example), OS switches to another job Timesharing (multitasking) is logical extension in which CPU switches jobs so frequently that users can interact with each job while it is running, creating interactive computing  Response time should be < 1 second  Each user has at least one program executing in memory process  If several jobs ready to run at the same time  CPU scheduling  If processes don’t fit in memory, swapping moves them in and out to run  Virtual memory allows execution of processes not completely in memory Operating System Concepts – 9th Edition 1.26 Silberschatz, Galvin and Gagne ©2013