OS tutoring #1

2013.04.03ASL @ KAU

http://asl.kau.ac.krAerosystem Software Lab. @ Korea Aerospace Univ

Contents

What is operating system?

History of OS

Input / Output

Software polling

Interrupt

Memory mapped

Storage structure

Cache

Locality of reference

OS basics

Process structure


What is Operating System?

An Operating System is the interface between

the users and the hardware.

It implements a virtual machine that is easier to program

than bare hardware

1101011010101

MOV EAX, EBX



An Operating System is the interface between

the users and the hardware.

It implements a virtual machine that is easier to program

than bare hardware

1101011010101

MOV EAX, EBXA = B

return



An OS provides standard services (an interface)

which are implemented on the hardware.

Including Processes, CPU Scheduling, Memory managem

ent, File system, Networking…

UI

Device IO

Graphic

Network

File IO

UI

Device IO

Graphic

Network

File IO

UI

Device IO

Graphic

Network

File IO

UI

Device IO

Graphic

Network

File IO

UI

Device IO

Graphic

Network

File IO



An OS provides standard services (an interface)

which are implemented on the hardware.

Including Processes, CPU Scheduling, Memory managem

ent, File system, Networking…

UI

Device IO

Graphic

Network

File IO

UI

Device IO

Graphic

Network

File IO

UI

Device IO

Graphic

Network

File IO

UI

Device IO

Graphic

Network

File IO

UI

Device IO

Graphic

Network

File IO

System Call



Magician

Government4GB 2GB

xx


The Goal of OS

Convenient

Software engineering problem

Efficient

System engineering problem


Why study Operating System?

Abstraction

How do we give the users the illusion of infinity resource?

(CPU time, Memory, File space)

System Design

Tradeoff

Performance Convenience

Abstraction

Performance Simplicity

OS

Hardware Software

Functionality


History of OS (Phase 0)

HW is a very expensive experiment, No OS

One function at a time

Computation

I/O

User think/response

Program loaded via card deck



Hardware is expensive, Humans are cheap

Simple Batch processing

Load program

Run

Print result

Dump

Start

Load New Job

Execute Job

Next Job?

Wait for Jobs

Yes No



Overlapped CPU & I/O operations

CPU Don’t need to wait till I/O Finishes

More effective usage of Hardware



Multi-programmed batch system

Looks like programs are running simultaneously

Pick some jobs to run (scheduling)

Put jobs in memory (memory management)



Hardware is less expensive than before,

Humans are becoming expensive

Interactive Timesharing

Preemptive scheduling to maintain adequate response time

Avoid Thrashing (program swap in, out)

UNIX developed at Bell Lab



Hardware is very cheap, Humans are expensive

Personal Computer (Macintosh)

Return to simplicity

No more supporting

Multiprogramming

Concurrency

Protection



Hardware are very cheap, but speed has limit

Parallel

Multi-core processors

GPU

Distributed

Cluster

Grid

Cloud

Shared Memory

CPU CPU CPU

Computer

Computer

Computer

Computer


Other OS

Real-time Operating System

Often used as a control device in a dedicated application

Controlling scientific experiments

Medical imaging systems

Industrial control systems

And some display systems.

Well-defined fixed-time constraints.

Real-Time systems may be either hard or soft real-time

Hard real-time

Failure cause injury or loss of money

Soft real-time

Failure is not much critical than hard real-time


Input / Output

CPU and device controllers all use a common

bus for communication Data bus

Address bus

Control bus

Ex. Put your hands up!

Put : Control

Your hands : Address

Up : Data


I/O

Synchronous I/O

CPU execution waits while

I/O proceeds

Easy to implement

Ex. Software polling

Asynchronous I/O

I/O proceeds concurrently

with CPU execution

More effective I/O

Ex. Interrupt


I/O type (Software polling)

Software polling synchronous I/O

CPU starts an I/O operation, and continuously polls

(checks) that device until the I/O operation finishes

Device controller contains registers for communication

Input, Output Register

for data

Control Register

to tell it what to do

Status Register

to see what it’s done


I/O type (Interrupt)

Device controller has its own processor,

and executes asynchronously with CPU

Device controller puts an interrupt signal on the bus

when it needs CPU’s attention

When CPU receive an interrupt

1. It saves the CPU state and invokes the

appropriate interrupt handler using the

interrupt vector

2. Handler must save and restore

software state

3. CPU restores CPU state


I/O type (Interrupt)

Interrupt timeline

Trap (software generated interrupt)

Kernel mode

System call


I/O Type (Memory mapped I/O)

Direct Memory Access

I/O device can transfer block of data to / from memory

without going through CPU

CPU

Memory

I/O device

data data

I/O Command


Storage Structure

Memory is not much fast

as what we think

Tradeoff between

size and speed

So we use caching

Where to cache?

Cache up block requires a lot of time

than accessing memory

If cache miss ratio is high, no need to

use cache system

Locality of reference


Locality of Reference


Hardware, Software, Middleware


3 main process in Kernel

Scheduler

Multi-Tasking

Pager

Memory Management

Cache

Swapper

Virtual Memory


User mode, Kernel mode

Kernel has core functions.

User applications has algorithm for jobs.


Process structure

4 main area

Text

Program Code

Data

Global variable

Static variable

BSS

Heap

Stack

Function frame stack

Technology

OS tutoring #1