Operating System 운영체제 Ⓒ 서울공대 OSLab

Silberschatz, Galvin and Gagne  Operating System Concepts 연구실 : 302 동 324 호 전화 : 이메일 홈페이지 : dcslab.snu.ac.kr 내 course 참조 Office Hours: 화, 목 14:30 -15:30 or by appointment 염헌영 ( 컴퓨터공학부 교수 )

Silberschatz, Galvin and Gagne  Operating System Concepts 담당조교  김형석  302 동 호실  전화 :  이메일 :  Office Hours: 월, 수 2-3 시

Silberschatz, Galvin and Gagne  Operating System Concepts Course Information 교재 : (1) 주교재 : Silberschatz, P. Galvin & G. Gagne, Applied Operating System Concepts, First Ed., (Windows XP Update), Wiley. (2) 참고도서 : L. F. Bic & A. Shaw, Operating Systems Principles, Prentice-Hall.

Silberschatz, Galvin and Gagne  Operating System Concepts Course Information 평가 중간고사 (4 월 말 예정 ): 30% 기말고사 (6 월 초 예정 ): 60% 출석 및 기타 : 10% ( 부정기적 Quiz 등 )

Silberschatz, Galvin and Gagne  Operating System Concepts Chapter 1: Introduction What is an Operating System? Mainframe Systems Desktop Systems Multiprocessor Systems Distributed Systems Clustered System Real -Time Systems Handheld Systems Computing Environments

Silberschatz, Galvin and Gagne  Operating System Concepts 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  Make solving user problems easier.  Make the computer system convenient to use.  Use hardware in an efficient manner. “Performance”  Throughput---jobs / sec.system oriented  Utilization---% of time busysystem oriented  Response time---sec / jobuser oriented  user oriented index conflicts with system oriented indices  user (R) 보다 system (U, T) 이 소중하면 batch 로 처리 (eg 동회 )  어떤 작업은 그 자체가 결정 ( 전화요금 – batch) (Web – 즉시처리 ) User OS HW

Silberschatz, Galvin and Gagne  Operating System Concepts Computer System Components 1. Hardware – provides basic computing resources (CPU, memory, I/O devices, …). 2. Operating system – controls and coordinates the use of the hardware among the various application programs for the various users. 3. Applications programs – define the ways in which the system resources are used to solve the computing problems of the users (compilers, database systems, games, business programs). 4. Users (people, machines, other computers).

Silberschatz, Galvin and Gagne  Operating System Concepts Abstract View of System Components

Silberschatz, Galvin and Gagne  Operating System Concepts Operating System Definitions Definition 1 -- Resource allocator  manages and allocates resources. Definition 2 -- Control program  controls the execution of user programs and operations of I/O devices . Definition 3 -- Kernel  one program running at all times  memory resident all the time  all else depend on this program.

Silberschatz, Galvin and Gagne  Operating System Concepts Mainframe Systems Batch:  동회 인감증명 (system 위주, batch 처리의 사례 )  쌓이면  서류창고  복사  수입인지  서류 창고  대장기록  여러 사람 것을 한꺼번에 모아 (batch) 처리  자원의 절약 -- by batching similar jobs  Batch 이전의 초기 컴퓨터 (card reader, 프린터 …)  Load compiler from card reader into main memory  Put Bob’s source program (punch card) on card reader  Run Compiler, which reads Bob’s program from card reader  Generate Bob’s binary to card puncher  Batch 시스템의 등장 – 당시에는 user 보다 HW 가 더 중요 (VLSI 이전 )  Compile in batch (many source programs are on card reader) Automatic job sequencing  automatically transfers control from one job to another.  First rudimentary operating system. Job Control -- (load cc, read src, compile, load bin, run, output 처리 …) Resident monitor  initial control in monitor  Job control (load, run)  When a user job completes -- control transfers back to monitor

Silberschatz, Galvin and Gagne  Operating System Concepts Memory Layout for a Simple Batch System Monitor CPU is idle While I/O is in progress Card Reader Printer

Silberschatz, Galvin and Gagne  Operating System Concepts Multiprogrammed Batch Systems Several jobs are kept in main memory at the same time, and the CPU is multiplexed among them. CPU tape… CPUNetwork CPU

Silberschatz, Galvin and Gagne  Operating System Concepts OS Features Needed for Multiprogramming I/O routine supplied by the system. Memory management –  the system must allocate the memory to several jobs.  할당되는 크기, memory 를 할당하는 순서 CPU scheduling –  must choose among several jobs ready to run on CPU  순서 Allocation of devices.  순서

Silberschatz, Galvin and Gagne  Operating System Concepts Time-Sharing Systems–Interactive Computin (multi-user system) -The CPU is multiplexed among several jobs that are kept in memory and on disk (not on card reader ! ) (the CPU is allocated to a job only if the job is in memory). -A job is swapped in and out of memory to the disk (not card reader).  Eg 한글 97, 탐색기  한가해지면 disk 로 (not card reader) -Users use (keyboard, mouse, CRT screen) to interact with program instead of (card reader, printer, etc). -On-line communication between the user and system is provided when the operating system finishes the execution of one command, OS asks next “control statement” from the user’s keyboard.  Eg 한글 97, 탐색기, …. -Response time should be short. (few seconds)  Users are given illusion that he is using the whole system.

Silberschatz, Galvin and Gagne  Operating System Concepts Desktop (PC) Systems Personal computers  computer system dedicated to a single user. I/O devices  keyboards, mice, display screens, personal printer  (from old system’s card readers, shared line printers) Goal change:  From  Maximum hardware utilization  To  User convenience and responsiveness ( 혼자서 HW 다사용 ). Do not need protection (Single user system)  Among users  Among user and system (minimum system is in ROM)  Vulnerable to worm, virus, etc. PC operating systems (Windows, MacOS, Linux)

Silberschatz, Galvin and Gagne  Operating System Concepts Real-Time Systems Eg: missile control, medical equipment control system. sensor system computer control Rigid response time requirement (milli-seconds 단위 or 더 빠름 ) Real-Time systems may be either hard or soft real-time.  Hard 절대로 지켜야 원자력 발전소 제어기  Soft 가급적 지켜야인터넷 강연, robot arm control

Silberschatz, Galvin and Gagne  Operating System Concepts Real-Time Systems (Cont.) Hard real-time:  Secondary storage limited or absent  (disk access time is not predictable)  data stored in memory  다른 OS 와 상이한 policy 를 사용해야  ( 일반 OS -- no response time guarantee)  general-purpose operating systems.  Timesharing Systems Soft real-time  Limited utility in industrial control of robotics  Useful in some applications (multimedia, virtual reality).

Silberschatz, Galvin and Gagne  Operating System Concepts Parallel Systems Multiprocessor system: Many CPU’s 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 (# of jobs / second)  Economical  Increased reliability  graceful degradation  fail-soft systems (fault tolerance – fault avoidance 와 비교 ) 용어 fault -- 고장자체 error – fault 의 파급효과

Silberschatz, Galvin and Gagne  Operating System Concepts Parallel Systems (Cont.) Symmetric multiprocessing (SMP)  Each processor runs 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 allocates work to slave processors.  More common in extremely large systems

Silberschatz, Galvin and Gagne  Operating System Concepts Symmetric Multiprocessing Architecture

Silberschatz, Galvin and Gagne  Operating System Concepts 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 ( 다른 노드에 있는 자원 활용 )  illusion that there is only one OS  Computation speed up – load sharing  Reliability  Communications

Silberschatz, Galvin and Gagne  Operating System Concepts Distributed Systems (cont) Requires networking infrastructure.  Local area networks (LAN) or Wide area networks (WAN) Network Operating System  Each node (processor + OS) is autonomous  Aware of network

Silberschatz, Galvin and Gagne  Operating System Concepts General Structure of Client-Server

Silberschatz, Galvin and Gagne  Operating System Concepts Clustered Systems Clustering allows two or more systems to share storage. Provides high reliability. Asymmetric clustering:  one server runs the application while other servers standby. Symmetric clustering:  all N hosts are running the application.

Silberschatz, Galvin and Gagne  Operating System Concepts Handheld Systems Personal Digital Assistants (PDAs) Cellular telephones Issues:  Limited memory  Small display screens  Limited power  Slow processors 차세대 3G 무선전화기

Silberschatz, Galvin and Gagne  Operating System Concepts Migration of Operating-System Concepts and Features

Silberschatz, Galvin and Gagne  Operating System Concepts Computing Environments Traditional computing Web-Based Computing Embedded Computing