CS 217 - Operating Systems Lectutre-01 Introduction and Overview Somia Razzaq NFC IET.

CS 217 - Operating SystemsLectutre-01Introduction and Overview

Somia RazzaqNFC IET

Goals for today• What is an Operating System?

▫ And – what is it not?

• Why study Operating Systems?

• How the course will proceed?▫ Course content▫ Grading▫ Regulations

Interaction is important!Ask Questions!

Note: Some slides and/or pictures in the following lectures are adapted from author slides by Silberschatz, Galvin, and Gagne and some from different instructor lectures taken from internet.

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Computer System

1. Hardware 2. Operating system 3. Applications programs 4. Users

Purpose of a Computer System

•Computer systems consist of software and hardware that are combined to provide a tool to solve specific problems in an efficient manner

•Execute programs

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Layered View of a Computer System

Computer System Hardware

Keyboard Mouse

PrinterRAM/ROM

HDMemBus

System Bus

Monitor

CD

Processor

Floating PointUnit

IntegerUnit

Cache

ControlUnit

What is an Operating System?•A program that acts as an intermediary

between a user of a computer and the computer hardware

•A program that allocates and de-allocates computer system resources in an efficient, fair, and secure manner—a resource manager

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Goals of Operating System

•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

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Technology Trends: Moore’s Law

2X transistors/Chip Every 1.5 years

Called “Moore’s Law”

Moore’s Law

Microprocessors have become smaller, denser, and more powerful.

Gordon Moore (co-founder of Intel) predicted in 1965 that the transistor density of semiconductor chips would double roughly every 18 months.

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ManyCore Chips: The future is here

• “ManyCore” refers to many processors/chip▫ 64? 128? Hard to say exact boundary

• How to program these?▫ Use 2 CPUs for video/audio▫ Use 1 for word processor, 1 for browser▫ 76 for virus checking???

• Parallelism must be exploited at all levels

• Intel 80-core multicore chip (Feb 2007)– 80 simple cores– Two floating point engines /core– Mesh-like "network-on-a-chip“– 100 million transistors– 65nm feature size

Frequency Voltage Power Bandwidth Performance3.16 GHz 0.95 V 62W 1.62 Terabits/s 1.01

Teraflops5.1 GHz 1.2 V 175W 2.61 Terabits/s 1.63

Teraflops5.7 GHz 1.35 V 265W 2.92 Terabits/s 1.81

Teraflops

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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

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Functionality comes with great complexity!

Proc

CachesBusses

Memory

I/O Devices:

Controllers

adapters

DisksDisplaysKeyboards

Networks

Pentium IV Chipset

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Sample of Computer Architecture Topics

Instruction Set Architecture

Pipelining, Hazard Resolution,Superscalar, Reordering, Prediction, Speculation,Vector, Dynamic Compilation

Addressing,Protection,Exception Handling

L1 Cache

L2 Cache

DRAM

Disks, WORM, Tape

Coherence,Bandwidth,Latency

Emerging TechnologiesInterleavingBus protocols

RAID

VLSI

Input/Output and Storage

MemoryHierarchy

Pipelining and Instruction Level Parallelism

NetworkCommunication

Oth

er

Pro

cess

ors

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Example: Some Mars Rover (“Pathfinder”) Requirements• Pathfinder hardware limitations/complexity:

▫ 20Mhz processor, 128MB of DRAM, VxWorks OS ▫ cameras, scientific instruments, batteries,

solar panels, and locomotion equipment▫ Many independent processes work together

• Can’t hit reset button very easily!▫ Must reboot itself if necessary▫ Must always be able to receive commands from Earth

• Individual Programs must not interfere▫ Better not crash antenna positioning software!

• Further, all software may crash occasionally▫ Automatic restart with diagnostics sent to Earth▫ Periodic checkpoint of results saved?

• Certain functions time critical:▫ Need to stop before hitting something▫ Must track orbit of Earth for communication

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Why processor is so limited?

What if you had to move the rover paying attention to every little component? Taking care of the motors, measuring soil/distances, coordinating with the controller at Earth…!

How do we tame complexity?• Every piece of computer hardware is different

▫ Different CPU Pentium, PowerPC, ColdFire, ARM, MIPS

▫ Different amounts of memory, disk, …▫ Different types of devices

Mice, Keyboards, Sensors, Cameras, Fingerprint readers▫ Different networking environment

Cable, DSL, Wireless, Firewalls,…

• Questions:▫ Does the programmer need to write a single program that

performs many independent activities?▫ Does every program have to be altered for every piece of

hardware?▫ Does a faulty program crash everything?▫ Does every program have access to all hardware?

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OS Tool: Virtual Machine Abstraction

• Software Engineering Problem:

▫ Turn hardware/software quirks

what programmers want/need

▫ Optimize for convenience, utilization, security, reliability, etc…

• For Any OS area (e.g. file systems, virtual memory, networking,

scheduling):

▫ What’s the hardware interface? (physical reality)

▫ What’s the application interface? (nicer abstraction)

Application

Operating System

HardwarePhysical Machine Interface

Virtual Machine Interface

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What does an Operating System do?• Silerschatz and Galvin:

“An OS is Similar to a government”▫ Begs the question: does a government do anything useful by

itself?• Coordinator and Traffic Cop:

▫ Manages all resources▫ Settles conflicting requests for resources▫ Prevents errors and improper use of the computer

• Facilitator:▫ Provides facilities that everyone needs▫ Standard Libraries, Windowing systems▫ Make application programming easier, faster, less error-

prone• Some features reflect both tasks:

▫ E.g. File system is needed by everyone (Facilitator)▫ But File system must be Protected (Traffic Cop)

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So what is this course all about?

• What we’ll be covering? and

• How we shall proceed?

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Tentative Course OutlineWeek # Module Topics

1 Introduction Introduction to the course Operating System Concepts System Structures

2 Process Concepts Process Concepts Process Scheduling Process Operations Inter process Communication Communication in Client Server Systems

3 Multithreaded Programming

Overview Multithreading Models Thread Libraries

4 Process Scheduling Basic Concepts Scheduling Criteria Scheduling Algorithms Thread Scheduling

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Course OutlineWeek # Module Topics

5 Synchronization Overview Critical Section Problem Semaphores Monitors

6 Deadlocks System Model Deadlock Characterization Methods for handling Deadlocks Deadlock Prevention

7 Memory Management Background Swapping Contiguous Memory Allocation Paging

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Course OutlineWeek # Module Topics

8 Mid Term Exam

9 Virtual Memory Demand Paging Copy-on-Write Page Replacement Allocation of Frames Thrashing

10 File System File Concept Access Methods Directory and Disk Structure File System Mounting

11-12 Secondary Storage Structure Overview of Mass Storage Structure Disk Structure Disk Scheduling RAID Structure Overview

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Course OutlineWeek # Module Topics12-13 I/O Systems Overview

Hardware Application I/O Interface Kernel I/O Subsystem Transforming Requests to Hardware Operations Streams

13-14 Protection Goals Principles Domain Access Matrix Access Control

15 Security The issue Threats Cryptography Authentication Defense

16 Distributed Operating Systems

An overview of Distributed Operating System Concepts

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Tentative Lab Exercise Plan

Lab # Module WeekLab 1 Process Creation in Java

RMI Example (Optional)Week 2

Lab 2 Threads in Java Week 3

Lab 3 Threads in Java (priority scheduling example) Week4

Lab 4 Synchronization in Java Week 5

Lab 5 Deadlock Example with handling of deadlocks in Java Week 6

Lab 6 Memory Management Exercise Week 8

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Textbook

• Operating System Concepts – 7/8th Edition

Silberschatz, Galvin, and Gagne (Textbook)

• Modern Operating Systems,3rd Edition,

Tanenbaum A.S., 2008 (Reference)

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Grading Scheme

• Quizzes 5% (unannounced/announced)

• Assignment 5%

• Attendance/

Class participation 5%

• Midterm Exam: 30%

• Final Exam: 50%

• Term Assignment 5%

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Academic Dishonesty Policy

• Copying all or part of another person's work, or using reference material not specifically allowed, are forms of cheating and will not be tolerated. A student involved in an incident of cheating will be subject to strict disciplinary action as per the institute’s policies.

• The instructor may take actions such as:

▫ require repetition of the subject work,

▫ assign a'zero' grade to the subject work,

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Remember

•Interaction is important!

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