Operating Systems
Vivek Pai
Lecture 1
Sep 13, 2001

Introduction
Who I am
 Vivek Pai
 PhD 99/00, Rice
 Research: OS, networking, highperformance apps
Why I do this
 Fun
 Interesting


Design opportunities
“Profitable”
Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 2

About this course…
Principles
 OS design
 Some theory
 Rationale
 Practice
Goals



Understand OS decisions
Basis for future learning
Get hands dirty
Not trade school Not “elite hacker”
Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 3

Expect (Some) Pain
Fast 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 4

What Works & Doesn’t
Works
 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 5

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 6

Some Relief
Grades 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 7

There Is No Magic
This Is Engineering Nothing’s Permanent
 Tradeoffs
 Constraints
 Optimizations
 Imperfection
 High rate of change
 Lots of inertia
 Cost/benefit analyses
 Human error
Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 8

Mechanics – Info
 My home page
 Course home page
 Newsgroup
 Precepts
 Design reviews
Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 9

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 10

Mechanics – People
Vivek Pai, room 322
8-2086, vivek@cs
Office hours: after class
Precept time/location
TBA
Brian Lai, room 414
8-5388, lai@cs
Office hours: TBA
Ping Ruan, room 217
8-0451, ryuan@cs
Office hours: TBA
Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 11

Mechanics – Readings
Operating System Design & Implementation
Tannenbaum & Woodhill, 2 nd 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 12

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 13

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 14

What Is an OS?
Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 15

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 16

What Is an OS?
Resources
 Allocation
 Protection
 Reclamation
 Virtualization
Services
 Abstraction
 Simplification
 Convenience
 Standardization
Sep 13, 2001
Makes computers simpler
COS 318 - Operating Systems, Vivek Pai 17

What Is an OS?
Resources
 Allocation
 Protection
 Reclamation
 Virtualization
Sep 13, 2001
Finite resources
Competing demands
Examples:
 CPU
 Memory
 Disk
 Network
COS 318 - Operating Systems, Vivek Pai 18

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

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 20

What Is an OS?
Resources
 Allocation
 Protection
 Reclamation
 Virtualization
Illusion of infinite, private resources
Memory versus disk
Timeshared CPU
More extreme cases possible (& exist)
COS 318 - Operating Systems, Vivek Pai 21 Sep 13, 2001

Mechanism & Policy
Mechanism – 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 22

Is There a Perfect OS?
Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 23

Is Any OS Complete?
Portability
Security
Fairness
Robustness
Efficiency
Interfaces
Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 24

History Lessons
60’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 25

Historical Comparison
Mainframe Mini Micro
System $/ worker
Goal
Target
10:1 –
100:1
System utilization
10:1
1:1
Overall cost
– 1:10-1:100
Productivity
Capacity Features Ease of
Use
Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai 26

Constant Employment?
 New hardware
 New features
 New approaches
Examples: Palm, Java, WWW
27 Sep 13, 2001 COS 318 - Operating Systems, Vivek Pai

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 28

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