Lesson 1 - Introduction.pdf

Chapter 1: Introduction Operating System Concepts – 9th Edit9on Silberschatz, Galvin and Gagne ©2013  Chapter 1: Introduction What Operating Systems Do Computer-System Architecture Operating-System Structure Operating-System...

Chapter 1: Introduction Operating System Concepts – 9th Edit9on Silberschatz, Galvin and Gagne ©2013  Chapter 1: Introduction What Operating Systems Do Computer-System Architecture Operating-System Structure Operating-System Operations Storage Management Operating System Concepts – 9th Edition 1.2 Silberschatz, Galvin and Gagne ©2013  Objectives To describe the basic architecture of computer systems To provide a grand tour of the major components of operating systems To give an overview of the many types of computing environments Operating System Concepts – 9th Edition 1.3 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 1.4 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 1.5 Silberschatz, Galvin and Gagne ©2013  Four Components of a Computer System Operating System Concepts – 9th Edition 1.6 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 Users of dedicate systems such as workstations have dedicated resources but frequently use shared resources from servers 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 1.7 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 1.8 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  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 OS 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  OS indexes into I/O device table to determine device status and to modify table entry to include interrupt Operating System Concepts – 9th Edition 1.12 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 1.13 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 1.14 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 1.15 Silberschatz, Galvin and Gagne ©2013  Storage-Device Hierarchy Operating System Concepts – 9th Edition 1.16 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 management important design problem  Cache size and replacement policy Operating System Concepts – 9th Edition 1.17 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  Advantages include: 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 specie task. 2. Symmetric Multiprocessing – each processor performs all tasks Operating System Concepts – 9th Edition 1.18 Silberschatz, Galvin and Gagne ©2013  Symmetric Multiprocessing Architecture Operating System Concepts – 9th Edition 1.19 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 1.20 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 1.21 Silberschatz, Galvin and Gagne ©2013  Clustered Systems Operating System Concepts – 9th Edition 1.22 Silberschatz, Galvin and Gagne ©2013  Computing Environments - Traditional Stand-alone general purpose machines Portals provide web access to internal systems Network computers (thin clients) are like Web terminals Mobile computers interconnect via wireless networks Networking becoming ubiquitous – even home systems use firewalls to protect home computers from Internet attacks Operating System Concepts – 9th Edition 1.23 Silberschatz, Galvin and Gagne ©2013  Computing Environments - Mobile Handheld smartphones, tablets, etc What is the functional difference between them and a “traditional” laptop? Extra feature – more OS features (GPS, gyroscope) Allows new types of apps like augmented reality Use IEEE 802.11 wireless, or cellular data networks for connectivity Leaders are Apple iOS and Google Android Operating System Concepts – 9th Edition 1.24 Silberschatz, Galvin and Gagne ©2013  Computing Environments – Distributed Distributed computiing  Collection of separate, possibly heterogeneous, systems networked together  Network is a communications path, TCP/IP most common – Local Area Network (LAN) – Wide Area Network (WAN) – Metropolitan Area Network (MAN) – Personal Area Network (PAN)  Network Operating System provides features between systems across network  Communication scheme allows systems to exchange messages  Illusion of a single system Operating System Concepts – 9th Edition 1.25 Silberschatz, Galvin and Gagne ©2013  Computing Environments – Client-Server Client-Server Computing  Dumb terminals supplanted by smart PCs  Many systems now servers, responding to requests generated by clients  Compute-server system provides an interface to client to request services (i.e., database)  File-server system provides interface for clients to store and retrieve files Operating System Concepts – 9th Edition 1.26 Silberschatz, Galvin and Gagne ©2013  Computing Environments - Peer-to-Peer Another model of distributed system P2P does not distinguish clients and servers  Instead all nodes are considered peers  May each act as client, server or both  Node must join P2P network  Registers its service with central lookup service on network, or  Broadcast request for service and respond to requests for service via discovery protocol  Examples include Napster and Gnutella, Voice over IP (VoIP) such as Skype Operating System Concepts – 9th Edition 1.27 Silberschatz, Galvin and Gagne ©2013  Computing Environments - Virtualization Allows operating systems to run applications within other OSes  Vast and growing industry Emulation used when source CPU type different from target type (i.e. PowerPC to Intel x86)  Generally slowest method  When computer language not compiled to native code – Interpretation Virtualization – OS natively compiled for CPU, running guest OSes also natively compiled  Consider VMware running WinXP guests, each running applications, all on native WinXP host OS  VMM (virtual machine Manager) provides virtualization services Operating System Concepts – 9th Edition 1.28 Silberschatz, Galvin and Gagne ©2013  Computing Environments - Virtualization Use cases involve laptops and desktops running multiple OSes for exploration or compatibility  Apple laptop running Mac OS X host, Windows as a guest  Developing apps for multiple OSes without having multiple systems  QA testing applications without having multiple systems  Executing and managing compute environments within data centers VMM can run natively, in which case they are also the host  There is no general purpose host then (VMware ESX and Citrix XenServer) Operating System Concepts – 9th Edition 1.29 Silberschatz, Galvin and Gagne ©2013  Computing Environments - Virtualization Operating System Concepts – 9th Edition 1.30 Silberschatz, Galvin and Gagne ©2013  Computing Environments – Cloud Computing Delivers computing, storage, even apps as a service across a network Logical extension of virtualization because it uses virtualization as the base for it functionality.  Amazon EC2 has thousands of servers, millions of virtual machines, petabytes of storage available across the Internet, pay based on usage Many types  Public cloud – available via Internet to anyone willing to pay  Private cloud – run by a company for the company’s own use  Hybrid cloud – includes both public and private cloud components  Software as a Service (SaaS) – one or more applications available via the Internet (i.e., word processor)  Platform as a Service (PaaS) – software stack ready for application use via the Internet (i.e., a database server)  Infrastructure as a Service (IaaS) – servers or storage available over Internet (i.e., storage available for backup use) Operating System Concepts – 9th Edition 1.31 Silberschatz, Galvin and Gagne ©2013  Computing Environments – Cloud Computing Cloud computing environments composed of traditional OSes, plus VMMs, plus cloud management tools  Internet connectivity requires security like firewalls  Load balancers spread traffic across multiple applications Operating System Concepts – 9th Edition 1.32 Silberschatz, Galvin and Gagne ©2013  End of Chapter 1 Operating System Concepts – 9th Edit9on Silberschatz, Galvin and Gagne ©2013  References https://www.os-book.com/OS9/?fbclid=IwAR1JyRs- n2Q5mj7zNUC1Ik1_7jK44XoDO79mO4yiJtNJh150Pen7bIu-osM http://www.nesoacademy.org/ Operating System Concepts – 9th Edition 1.34 Silberschatz, Galvin and Gagne ©2013