Operating Systems

Vivek Pai

Lecture 1

Sep 13, 2001

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 2

IntroductionWho I am

Vivek Pai PhD 99/00, Rice Research: OS,

networking, high-performance apps

Why I do this

Fun Interesting Design

opportunities “Profitable”

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 3

About this course…Principles

OS design Some theory Rationale Practice

Not trade school

Goals

Understand OS decisions

Basis for future learning

Get hands dirty

Not “elite hacker”

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 4

Expect (Some) PainFast pace

Lots of projects (programming)

Hard material

Course changing based on feedback

Not the end of the world – course favorably received last year, under much more trying circumstances

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 5

What Works & Doesn’tWorks Solid C background Flexible approach Grasping Prereqs Open mind Einsten Feedback sheets

Doesn’t Schedule overload Missing background Mathematical

precision

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 6

Why So Many Grades? Programming projects Midterm & final exams Quizzes (see me about health/school absences)

Intended to reduce pressure/anxiety

More data points = less noise

Fairly generous extra credit

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 7

Some ReliefGrades based on

mean/deviation

People did generally well last time

38 As

11 Bs

7 Cs

Honor System Use common sense Ask for clarification Cooperation OK Work is your own

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 8

There Is No MagicThis Is Engineering

Tradeoffs Constraints Optimizations Imperfection

Nothing’s Permanent

High rate of change Lots of inertia Cost/benefit

analyses Human error

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 9

Mechanics – Info My home page Course home page Newsgroup Precepts Design reviews

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 10

Mechanics – Grading Assigned readings 15% participation (quizzes) 15% midterm 15% final 55% projects Some extra credit Late policy TBA

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 11

Mechanics – PeopleVivek Pai, room 3228-2086, vivek@csOffice hours: after class

Brian Lai, room 4148-5388, lai@csOffice hours: TBA

Ping Ruan, room 2178-0451, ryuan@csOffice hours: TBA

Precept time/location

TBA

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 12

Mechanics – ReadingsOperating System Design & Implementation

Tannenbaum & Woodhill, 2nd Edition

Same as last time

Available at Ustore

Various readings – will be available from my home page (course web site)

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 13

Mechanics - Projects 6 projects, 2 themes

– Build parts of a mini-OS– Write applications that interact with OS

2 weeks each Uses Linux, sort of Partners – be decent to each other

Option – one big project – only for the brave

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 14

Send Me Your Details Name Year Major E-mail address Phone # Picture via URL Why you’re taking the class What you’d like/hope to learn

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 15

What Is an OS?

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 16

What Is an OS?“Code” that:

Sits between programs & hardware Sits between different programs Sits betweens different users

But what does it do?

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 17

What Is an OS?Resources Allocation Protection Reclamation Virtualization

Services Abstraction Simplification Convenience Standardization

Makes computers simpler

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 18

What Is an OS?Resources Allocation Protection Reclamation Virtualization

Finite resources

Competing demands

Examples: CPU Memory Disk Network

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 19

What Is an OS?Resources Allocation Protection Reclamation Virtualization

You can’t hurt me

I can’t hurt you

Implies some degree of safety & security

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 20

What Is an OS?Resources Allocation Protection Reclamation Virtualization

The OS giveth

The OS taketh away

Voluntary at run time

Implied at termination

Involuntary

Cooperative

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 21

What Is an OS?Resources Allocation Protection Reclamation Virtualization

Illusion of infinite, private resources

Memory versus disk

Timeshared CPU

More extreme cases possible (& exist)

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 22

Mechanism & PolicyMechanism – tool to achieve some effect

Policy – decisions on how to use tool

Examples: All users treated equally All program instances treated equally Preferred users treated better No deterministic behavior at all

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 23

Is There a Perfect OS?

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 24

Is Any OS Complete?Portability

Security

Fairness

Robustness

Efficiency

Interfaces

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 25

History Lessons60’s-70’s - Mainframes Rise of IBM

70’s - 80’s – Minicomputers Rise of Digital Equipment

80’s - 90’s – PCs Rise of Intel, Microsoft

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 26

Historical ComparisonMainframe Mini Micro

System $/

worker

10:1 – 100:1

10:1 – 1:1

1:10-1:100

Goal System utilization

Overall cost

Productivity

Target Capacity Features Ease of Use

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 27

Constant Employment? New hardware New features New approaches

Examples: Palm, Java, WWW

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 28

May You Live in Interesting Times…

Processors double in 18 months Disk doubling every 12 months Global bandwidth every 6 months “Sweet spot” constantly decaying

Do people ever double?

Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 29

Send To vivek@cs… Name Year Major E-mail address Phone # Picture via URL Why you’re taking the class What you’d like/hope to learn

Consider this a grade