Operating Systems - Drexel CCIbmitchell/course/mcs720/intro.pdfIntroduction Brian Mitchell ([email protected]) - Operating Systems 27 Operating System Components • Process

Brian Mitchell ([email protected]) - Operating Systems 1Introduction

Introduction

Operating Systems

User

Programs

OS

Interface

Kernel &DeviceDrivers


Introduction

• Instructor Brian Mitchell - “Brian”

[email protected]/~bmitchel

• TA - To Be Announced• Course Information

MCS720 – Tuesday’s 6 - 9 PM

• Online Information www.mcs.drexel.edu/~bmitchel/course/mcs720

Please check course web page several times per week. The web page will be my primary mechanism for communicating:

Special and Emergency Information (posted by 12:00 noon on day of the class)

Syllabus Assignments Exam Information Solutions to Problems


Introduction

• Course Objective– To investigate classical internal algorithms

and structures of operating systems– Machine Architectures– Concurrent Programming

• Textbook Applied Operating Systems Concepts, Avi

Silberschatz, Peter Galvin, Greg Gagne

• Additional References Modern Operating Systems, Andrew

Tanenbaum

Distributed Operating Systems, Andrew Tanenbaum

Selected research papers


Introduction

• Homework’s, Projects, Exams Programming Projects: This course will

include a significant project that can be worked on individually or in teams. Specifications for the project are on the course web page.

Research Presentation: This course will require you review research papers related to operating systems, as well as present a paper that you select to the class.

Final: There will be a 90 minute final exam


Course Topics

• Introduction• Processes & Threads• Process Synchronization• CPU Scheduling• Memory Management• Virtual Memory• Deadlock• File and I/O Systems• Directory Services• Security and Protection• Operating System Case Studies• Special Purpose Operating Systems

– Embedded– JavaOS– WebOS


User Programs

Project Introduction

• Learn about the internals of operating systems, operating system algorithms, and operating system and hardware integration.

• Goal: Construct a simulated:– Hardware– Operating System– Assembler

OperatingSystem

Hardware



• Sample Programming Language– Simple, pseudo-assembler based– Instructions:

• Nop, alm, frm, cmp, jeq, jgt, jlt, jge, jle, clr, inc, dec, add, sub, mul, div, mov, and, or, not, xor, hlt, dis

start: alm R1,d500 ;allocate 500 bytes mov R2,#0 ;R2 will hold our offset

looptop: mov (R1)+R2,R2 ;update memory location;with value

inc R2 ;increment R2 cmp R2,d500 ;compare R2 to 500 jlt looptop ;if R2<500 go to looptophalt ;stop execution

Sample Program



• Processing the programs

Get Instruction

Validate Instruction

Fetch and resolve opcode arguments (if any)

Execute Instruction

Check and Handle Faults (if any)

Log Instruction Results in the Hardware Trace

FIRST INSTRUCTION

NEX

T IN

STR

UC

TIO

N



• OS Memory Manager– Linked Lists– First, best, next, worst fit allocation

algorithm– Interface with the page table in hardware– Handle program and page faults– Provide interface to user programs who

require memory– Interface with hardware to manage the

memory



• Simulated hardware

General Purpose Registers

R1 R2 R3 R4 R5 R6 R7 R8

Control Registers

C T PF PC

TLB*

CACHE*

PAGETABLE

Physical Memory SWAP Space


Project Information

• Getting Started– Sample code and ant (www.apache.org)

script is provided in the project page


Introduction

• Grading– The following distribution will be used to

determine your final grade in this course:• 20%: Phase 1 Project Deliverable• 10%: Phase 2 Project Deliverable• 30%: Phase 3 Project Deliverable• 20%: Research Paper Presentation• 20%: Final Exam

• Policies– Policies governing the project are described

on the project web page. – Makeup exams will take the form of an

oral exam or an alternative test (in-class or take-home).


Introduction

• Computer hardware requires software to perform useful operations

• Types of software– Systems Programs: manage the operation of

the computer itself– Application Programs: solve user problems

• The Operating System (OS) is the most fundamental of all systems programs– OS controls ALL of the computers resources– OS provides VALUABLE services to user

programs– OS COORDINATES the execution of user

programs– OS PROVIDES resources to user programs


Computer Systems Structure

• Modern computer systems consist of:– One or more processors– Main memory– Clocks (Synchronization, coordination)– Terminals– Disks– Network Interfaces– Input/Output Devices

• Systems Architectures– SISD, SIMD, MIMD, MISD

(we will look at these later)• Processor Organization

– Single Processor– Multiprocessor– Symmetric Multiprocessor– Distributed– Clusters


Rationale for OS

• Directly interfacing user programs with hardware is COMPLEX

• Building programs for specific computer architectures is not portable

• If every program included code to interface with the computer hardware– Redundancy– Inconsistent quality– Inefficient use of resources

• DESIRE => Shield programmers from the complexity of the hardware– OS is a layer that sits on top of the

hardware– OS provides an interface or virtual

machine that is easy to understand and program


OS Architecture

• Most Operating Systems use a layered architecture

Physical Devices

Microprogramming

Machine Language

Operating System

Compilers Editors CommandInterpreter

BankingSystem

AirlineReservation

WordProcessor U

SER

SYST

EM

HA

RD

WA

RE


OS Architecture (con’t)

• Physical Devices– Computer hardware - CPU, memory, I/O

devices, network interfaces

• Microprogramming– ROM-based programs– Controls CISC processors

• Machine Language– Instructions supported by the hardware– Binary encoded– Processors typically support 50-300

instructions• CISC vs RISC

– Use registers as the basis for performing most operations

• Running programs• Device interfaces



• Operating Systems– Hide the complexity of software

• Read 200 bytes from file A versus managing the motor and arms of the disk drive

– Provide an interface for the programmer• Usually documented as a set of API’s

– ex: Win32 on Windows98 & WindowsNT– Win32 contains about 6,000 API’s– OpenFile(), CreateProcess(), ...

– Systems software usually sits on top of the kernel of the OS

• Command Interpreter, Security Manager, Utilities (e.g., awk, grep on Unix)

– Most processors support multiple execution modes

• Minimally Kernel/Supervisor and User modes



• Operating system runs in Kernel mode and user programs run in User mode

• Kernel Mode– Full access to machine instruction set– Direct access to hardware, memory, and

input/output devices– OS and device drivers must run in Kernel

mode

• User Mode– Access to a limited set of machine

instructions– No direct access to hardware, memory and

input/output devices• Device access is coordinated by OS

– Typically user mode instructions consist of computational instructions

• MS DOS only supported Kernel mode


OS Architecture - Summary

• Operating System acts as an extended machine from a user program perspective– Reduce complexity– Increase system integrity– Reduce redundancy

• Operating System acts as a resource manager– Hardware provides many resources to user

programs– Demand for resources may exceed resource

capacity– OS must optimally manage allocation of

the resources• Ex: Memory, Processor/CPU time


Example: Web Browser

WEB Browserhttp://www.mcs.drexel.edu

OperatingSystem

Socket API

DeviceDriver

TCP/IP Frames

Network InterfaceCard (NIC)

Memory-Mapped

Electrical Signals Network

User Mode

Switch to Kernel Mode

Kernel Mode


History of Operating Systems

• First Generation (1945-1955)– Hardware was tube-based– Programs were hardwired on plugboards– Hardware could run one program at a time– Applications: Numerical Calculations

• Second Generation (1955-1965)– Transistor-based– Assembler - improvement over machine

language– High Level Language - FORTRAN– Batch oriented

• Jobs were created on card or tape• Jobs were serially executed

– Scientific / Engineering applications– Early operating systems introduced

• Capabilities limited to controlling the serial execution of batch jobs



• Third Generation (1965-1980)– IC circuits (LSI, VLSI chips)– Business applications supported in addition

to scientific and engineering applications• Business Applications: IO-based• Engineering/Scientific Applications : CPU-

based

– OS supported several new capabilities• Multiprogramming

– Load multiple jobs into memory– When one job was waiting for I/O the OS

ran another job– Job spooling - queue of ready to run jobs

reduced operator intervention

• Timesharing– Support for multiple, concurrent users– OS timeslices user sessions– OS takes responsibility for maximizing

CPU and device utilization



• Fourth Generation (1980 - )– Workstations and PC’s– Computer networks become commonplace– CPU’s with millions of transistors offer

high computational power– Desire: User friendly software

Result: Complex operating systems– OS designed to scale and integrate well

with new computer architectures• Real time / Embedded• SMP• CISC, RISC• Parallel• Network

– OS address new concerns• Network transparency• Security



• Fifth Generation (2000? - ???? )– OS designed to support massively parallel

computer architectures• Thousands of CPU’s

– MPP architectures may consist of thousands of independent computers connected by high-speed networks

• ex: BISDN at 155Mbits/sec– MPP architectures may consist of processor

boards “plugged” into custom design backplanes

– One or multiple copies of the OS?– Issues

• Cache coherence• Management and coordination of

distributed resources• Bandwidth limitations• Keeping consistent time


Special Operating System Types

• Distributed Systems– Goal is to distribute the computation across

several physical processors– Can use either standard networks, or

proprietary inter-connection technologies– Advantages:

• Scalability at low cost• Reliability

– Disadvantages:• Programming is complex• Overhead may be large

• Real time systems– Typically used to control a device– Well defined time constraints must be

respected– General purpose operating systems do not

often handle the requirements of a real-time system


Operating System Components

• Process Management– A process is a program in execution– OS manages the creation and deletion of

processes

• Main-Memory Management– OS keeps track of memory in use and free

memory, who is using the memory, allocation and freeing of memory.

• Secondary-Storage Management– OS uses secondary storage to extend

physical memory– Secondary Storage typically resides on disk

• I/O System Management– OS uses the I/O system for management of

devices (device drivers)– Caching– Example: File System


Operating System Components

• File Management– OS Manages the creation and deletion of

files, and directories– OS also manages file system permissions

• Who owns the file, who can modify the file

• Protection System– Distinguish authorized versus non-

authorized usage of OS resources

• Networking– Enables OS users to utilize network

resources• Remote disks, Internet, shared printers, file

servers, email, …

• Command-Interpreter System, Graphical User Interfaces– Provides the user with an interface for

using the operating system facilities


Operating System Interfaces

• Operating Systems typically provide two interfaces:– User interfaces: Command Line

Interpreter, or graphical user interface– Program interfaces: OS provide interfaces

via application programming interfaces to programs.

• Sometimes called system calls

• System Calls– Operating system designers typically

package system calls as C language function calls

• Example: Win32 on Windows 95/98/NT– Most operating systems also provide

additional classes for better integration with object oriented languages such as C++

• Example: MFC on Windows 95/98/NT


Virtual Machines

• A virtual machine takes the layered approach to its logical conclusion. It treats hardware and the operating system kernel as though they were all hardware.

• A virtual machine provides an interface identical to the underlying bare hardware.

• The operating system creates the illusion of multiple processes, each executing on its own processor with its own (virtual) memory.

• Some operating systems (e.g., VM by IBM), work by running all processes in a virtual machine

• VM concepts are most widely applied in interpretive languages (e.g., Java)– Interface to the machine is facilitated by

the virtual machine

Documents

Operating Systems - Drexel CCIbmitchell/course/mcs720/intro.pdfIntroduction Brian Mitchell ([email protected]) - Operating Systems 27 Operating System Components • Process