CSC 326 Chapter 1, Spring 2016

Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9th Edit9on Chapter 1: Introduction 1.2 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9th Edition Four Components of a Computer System 1.3 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9th Edition 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 1.4 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9th Edition 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 1.5 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9th Edition 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  “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. 1.6 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9th Edition 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 1.7 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9th Edition 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 1.8 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9th Edition 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 1.9 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9th Edition 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 1.10 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9th Edition 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 1.11 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9th Edition Storage-Device Hierarchy 1.12 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9th Edition 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 1.13 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9th Edition 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. Increased reliability  Two types: 4 Asymmetric Multiprocessing – each processor is assigned a specie task. 4 Symmetric Multiprocessing – each processor performs all tasks 1.14 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9th Edition Symmetric Multiprocessing Architecture 1.15 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9th Edition A Dual-Core Design  Multi-chip and multicore  Systems containing all chips  Chassis containing multiple separate systems 1.16 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9th Edition 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 1.17 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9th Edition Clustered Systems 1.18 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9th Edition Operating System Structure  Multiprogramming 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 1.19 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9th Edition Memory Layout for Multiprogrammed System Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9th Edit9on End of Chapter 1