AOS01 Intro

8/8/2019 AOS01 Intro

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Advanced Operating System

By: Dr. M. Alam

Introduction

Advanced OS : Dr. M. Alam

Grading

? Attendance? 75% required

? Absence is marked after 10 minutes

? Assignments

? Late submission means 5% deduction per week

? Mid-term Exam.

? Presentation / Research Report

? Final Exam.


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1. Modern Operating Systems, Andrew S.Tanenbaum.

2. Distributed Systems, Andrew S. Tanenbaum.3. Operating Systems by William Stallings, 3rd

Edition.

4. Operating System Concepts, SilberschatzGalvin, 7th Edition

5. Distributed Systems : Concepts and Design,G. Coulouris, J. Dollimore & T. Kindberg

6. Internet websites .

Recommended Books


Course Outline

? Introduction? Communication

? Synchronization

? Processes & Scheduling

? File System

? Specific OS

? Research Work


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? Introduction of Operating System

? Computer Systems and Operating System

? Introduction ofAdvanced Systems

? Introduction of Distributed Operating System

? Exposure of existing operating systems : Unix,

Linux, Window NT,

? Discussion and implementation issues

Objectives


What is Operating System ?

? A program that acts as an intermediary between a

user of a computer and the computer hardware

? Provides facilities how to use the computer

? Layer of software on the top of bare H/W that

control & manage the resources

? Examples : UNIX, IRIX, LINUX, Windows, .

? Runs in kernel or supervisor mode / protected

from user


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How it works?

Example

Process Swapping in Time Sharing SystemsProcess Swapping in Time Sharing Systems

? System Calls

? Start process, Terminate process, Release memory,

? Process Table Entry

Application

Program

Extended Instructions

System Calls

Operating

System


Computer System

? Computer System Components?Hardware provides basic computing resources like

CPU, memory, I/O devices.

? OS controls & coordinates the use of hardware

among the various application programs for the

various users.

?Application programs define the ways in which the

system resources are used to solve the computing

problems of the users (Database systems, Video

games, Business programs).

? Users (People, Machines, Other computers)


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Computer System

User

Hardware

OS/KERNEL

System

Programs

Application/Shell? Functionality of OS

? Initializes H/W

? Provides device control

? Provides management, scheduling

& interaction of tasks

? Maintain system integrity

? Error handling

? Converts users commands to

machine language


Parts of OS

Generally a modern OS has four parts:

Operating System

SchedulerProcess

Manager

Kernel File

Manager


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User View of OS

? Standalone PC

? The operating system is designed for ease of use

? Little attention paid to performance

? None paid to resource utilization

? Mainframe or Minicomputer

? Operating system is designed to maximize resource utilization

? Users share resources like CPU, memory and I/O efficiently

? Workstations

? Users connected through network, have dedicated resources at

their disposal but shared as well

? The OS is designed to compromise between individual usability

and resource utilization


System View of OS

?

Resource Allocation? Computer System Resources- CPU, Clock, Memory,

Disks, Terminals, I/O devices,

? OS acts as a manager of these resources

? Manages & allocates resources to specific users andprograms so that it can operate efficiently and fairly

? Control Program

? Controls the execution of user programs and operationsof I/O devices.

?

Kernel? The one program running at all times


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Tasks of OS

? Process Control

? Memory Management

? File Systems & Management

? I/O Control

? Security

? Synchronization

? Communication


Computer Systems & OS


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Computer Systems

?Mainframe Systems

?Desktop Systems

?Multiprocessor Systems

?Clustered Systems

?Distributed Systems

?Real-Time Systems

?Handheld Systems


Mainframe Systems

? First computers used to tackle manycommercial and scientific applications

? Types of mainframe systems:

? Simple Batch Systems

? Multiprogramming Batch Systems

? Time-Sharing Systems


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Simple Batch Systems

? Input /Output Devices: Card Readers, TapeDrives, Line printers, Card Punches (Slower mechanical devices)

? Programmer/user prepare a job (program,data and control information)

? CPU often sits idle

? Similar jobs are batched together to speed upprocessing

? OS:

? Transfer control automatically betweenjobs

? Could perform job scheduling (due todirect access to several jobs on a disk )

? Always resident in memory

Memory Layout


Multiprogramming Batch Systems

Several jobs are kept in mainmemory at the same time andCPU is multiplexed

Operating System

Job 1

Job 2

Job 3

0

512K

OS Features

? I/O routines supplied by the system.

? Memory management the system must

allocate the memory to several jobs.

? CPU scheduling the system must

choose among several jobs ready to run.? Allocation of devices.


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Time-Sharing Systems

? The CPU is multiplexed among several jobs (CPUis allocated to a job only if the job is in memory).

? A job swapped in and out of memory to the disk.

? On-line communication between the user and thesystem is provided; when OS finishes theexecution of one command, it seeks the nextcontrol statement from the users keyboard.

? These systems involves memory management andprotection, file system, CPU scheduling, Jobsynchronization and communication, and avoiding

jobs to be deadlocked.


Desktop Systems

?Personal Computers System dedicated to asingle user.

? I/O devices Keyboards, Display screens,

Small Printers, ..

? User convenience and responsiveness.

? Do not need advanced CPU utilization or

protection features.

?

May run several different types of operatingsystems (Windows, MAC OS, UNIX, Linux)


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Multiprocessor / Parallel Systems

? Systems with more than one CPU in closecommunication.

? Tightly coupled system:

? Processors share memory and a clock

? communication usually takes place through theshared memory

? Advantages of parallel system:

? Increased Throughput

?Economical

? Increased Reliability


Fault Tolerant Mechanism

? System consists of two identical processors(primary and backup), each with its local memory.

? Processors are connected through a bus.

? During the execution of the system, the state

information of each job (including a copy of

memory image) is copied from primary to backup.

? In case of failure, backup copy is activated and

restart from the most recent checkpoint.

? An expensive solution as it involves considerablehardware duplication.


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Multiprocessing

? Symmetric Multiprocessing (SMP)

? Each processor runs an identical copy of the OS.

? Many processes can run at once without performance

deterioration.

? Most modern operating systems support SMP.

? Asymmetric Multiprocessing

? Each processor performs a specific task; master

processor schedules and allocate work to slave.

? More common in extremely large systems.

? The difference between SMP and Asymmetric MP

could be either hardware or software.


Distributed Systems

?

Distribute the computation among severalphysical processors.

?Loosely coupled system

? Each processor has its own local memory

? Processors communicate with each other through high-speed buses or switches or telephone lines.

? Requires networking infrastructure

? Local area networks (LAN) or

? Wide area networks (WAN)

? May be either client-server or peer-to-peersystems.


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Distributed Systems (Conti.)

? Advantages of distributed systems: Resource Sharing,

Computation Speedup, Load Sharing, Reliability,

? NetworkOS

? Provides file sharing? Provides communication schemes that allows different

processes on different computers to exchange messages.

? Runs independently from the other computers on the network.

? Distributed OS

? Less autonomy between computers

? Give the impression there is a single OS controlling the

network.


Clustered Systems

?

Combination of two or more systems (nodes)connected through S/W and network infrastructure

? Shared resources

? Processors communicate using message passing

? Cheaper with respect to high processing power

? Homogeneous Cluster

? All nodes have similar architecture and similar OS

? Heterogeneous Cluster

? Nodes have different architecture or different OS

?

No specific OS; OS is installed on all machines? Unavailability of general-purpose distributed file

system


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Real Time Systems

? Often used as a control device in a dedicatedapplication such as

? Controlling scientific experiments

? Medical imaging systems

? Industrial control systems

? Some display systems,

? Well-defined fixed-time constraints.

? Real-Time systems may be either

? hard or

? soft


Hard Real Time Systems

? Guarantees that critical tasks are completed on time

? Secondary storage is limited or absent, data is stored

in short term memory OR read-only memory (ROM)

? ROM will be nonvolatile storage device

? Most advance operating system operations are

absent

? Conflicts with time-sharing systems as most

advanced OS features are absent.

? Not supported by general-purpose operatingsystems.


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Soft Real Time Systems

? Less restrictive

? A critical real-time task gets priority

?

Limited utility in industrial control or robotics? Useful in applications (multimedia, virtual

reality) requiring advanced operating-system

features

? It is added to most recent Operating Systems

including major versions of UNIX


Handheld Systems

? Personal Digital Assistants (PDAs)

? Cellular Telephones

? Issues:

? Limited Memory

? Slow Processors

? Small Display Screens

? Smaller Bandwidth


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Working of Operating Systems


Starting of OS

? Turn on or restart the computer system, activates the

bootstrap loader

? Bootstrap

? Initializes the hardware (Interrupts)

? Read OS from somewhere ( Memory or disk or network )

? OS loads and starts a user-level 'init' program

? init starts an original collection of processes,

usually specified by a configuration file

?

typically including a login authorization program for eachterminal line or other input device


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Starting of OS (Continue)

? init also starts other 'daemon' processes such as

? Network management and services,

? Time service,

? Batch job manager,

? When user login to a terminal, the login process

? Creates ashellfor user as a sub-process.

? Then waits for the shell to terminate that is done

when user logoff

? In case ofrlogin, it is a network service daemon

that creates theshellfor user


Invoking a System Call

Steps involved to invoke a system call

Communication: User ? OS?

How to request the services?


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Structure of Operating Systems


Structure of Operating Systems

1. Monolithic System2. Layered System

3. Virtual Machines

4. Client-Server Model


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Monolithic System


Monolithic System

? OS is a collection of procedures (System Calls)? Procedures or files containing procedures are

compiled and then bind all together

? Dont care about information hiding

? Procedures can call each other freely

? Each procedure has well defined parameters &

results


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Model

Organized in Three Layers


Basic Organization

1. Main Procedure : Invokes services procedures2. Service Procedures : Carry out the system calls

3. Utility Procedures : Helps the service procedures

? One system call against one service procedure

? Utility procedures do job required by service

procedures (e,g. fetch data from user program)


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Functionality

1. User program request service by invoking system call

2. Procedure puts parameters in registers or on stack and

issues the trap instruction (Kernel or Supervisor call)

3. Machine switches from user mode to kernel mode4. Control is transfer to OS

5. OS checks parameters? Which system call ?

6. OS indexes to table that contains the pointer to required

procedure

7. Service procedure is identified and then called

8. System call is finished & control is given back to user

program


Layered System


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Layered System

Structure ofTHE (Technische Hogeschool Eindhoven)Operating System

? OS is organized as h ierarchy of six layers

? Simple batch system

The Operator5

User Programs4

I/O management3

Operator Process Communication2

Memory & Drum Management1

Processor Allocation & Multiprogramming0

?MULTICS ? Concentric Rings


Layer 0 & Layer 1

? Allocate processors? Switches between processes (When interrupts occur or

timer expiration)

? Multiprogramming : Sequential processes are

programmed without knowing that multiple processes

are running on a single processor

? Allocate space for processes in main memory

?

For larger process, extra part is placed on disk/drum? Responsible to bring pages into memory when needed

Layer 0

Layer 1


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Layer 2 & Layer 3

? Communicate between process & operator

console

? Each process has its own operator console

Layer 2

Layer 3

? Manages I/O devices

? Buffers information stream to & from I/O

? A process can handle abstract I/O devices nicely


Layer 4 & Layer 5

? Contains user programs

? User program do not need to bother about

process, memory, console or I/O management

Layer 5

Layer 4

? Contains system operator process


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Virtual Machine


Virtual Machines

? VM/370 based on observation that a timesharing system provides1. Multiprogramming and

2. An extended machine with more convenient interfacethan the bare H/W


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Virtual Machine Monitor (VMM)

? Performs multiprogramming

? Runs on bare H/W

? Provides several virtual machines to next layer.

? These are not extended machines with files & other

nice features but these are exact copies of bare H/W

(including kernel / user mode, I/O interrupts, & .

like real machine)

? Each virtual machine is identical, one can run any OS

that will run directly on H/W

? Different virtual machines may run different OS


Conversational Monitor System

? CMS executes system call

? Call is trapped to the OS in its own virtual

machine just like running on real machine

? Example: Read Data

? CMS issues hardware I/O instructions for reading

required data

? I/O instructions are trapped by VM/370

? VM treats instruction as part of simulation of the real

H/W


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Client-Server Model


Client-Server Model

? Goal: Develop most OS functions in user

processes & leavingminimal kernelin OS

? Invoking a service:

? User process (client process) sends request toserver process

? Then server process performs the job & sendresults

? Kernel

? Handle communication between clients andservers

? provides low-level resource management


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Basic Organization

? Modular Approach:

? Divide OS into parts

? Each part handles one module (set of specificservices) of the system

? Such as file service, process service, terminalservice, memory service,


Features

? Modular Approach is easier to understand

? Management is easier for smaller part

? Servers

? Run as user-mode process instead of kernel-mode

? Do not have direct access to H/W

? Any failure in a server will cause the crash in

that particular service not in the whole system


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Application in Distributed System

? Can be used in distributed systems

? Client communicate with server through messages

?

Client do not know that message is treated locallyor remotely

? Kernel conveys the messages only

Kernel

PE 4

Memory ServerClient

Kernel

PE 1

File Server

Kernel

PE 2

Process Server

Kernel

PE 3

Messaging


Summery

? What is an Operating System

? What is a Computer System

? How OS & computer system affect

each other


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Assignment

Write a brief report about an OS including itsdistinguished features & limitations

? Windows

?

DOS? IRIX

? Linux

? Unix

? Free BSD Unix

? Solaries

? ..


Research Topics

Choose a research paper/topic for writing the

report that you have to submit

? Deadlock Prevention

? Multiple Locks

? OS for Mobile Equipments

? Synchronization

? Scheduling

? .

Documents

AOS01 Intro