CS 3214Computer Systems

Godmar Back

Lecture 1

CS 3214 Fall 2010

About Me

• Undergraduate Work at Humboldt and Technical University Berlin

• PhD University of Utah• Postdoctoral Work at Stanford University• 7th Year at Virginia Tech

– joined August 2004, – Tenured Associate Professor since June 2010– 3rd time teaching this class

• Research Interests:– Systems

ADMINISTRIVIA

CS 3214 Fall 2010

CS 3214 Fall 2010

Course Facts

• Meet Tuesday & Thursday 11:00am-12:15pm (GBJ 102) • Check website regularly

– http://courses.cs.vt.edu/~cs3214

• Use CS Forum http://forum.cs.vt.edu/• Send email to

– cs3214-staff@cs.vt.edu• TAs:

– Scott Schneider– Puranjoy Bhattacharjee (50%)– Xiaomo Liu (50%)– Patrick Boyd (UTA)

• All students enrolled in CS3214 have access to McB 124 (Systems Lab)

CS 3214 Fall 2010

Email Etiquette

• Please enter your name in webmail so it appears in From: line

• Be coherent when you email

CS 3214 Fall 2010

Reading Material

• Required Textbook– Bryant and O’Hallaron

(2nd Edition), 2011– Will post reading

assignments

CS 3214 Fall 2010

Class Format

• Lectures• Exams

– 1 Midterm– 1 Final (Comprehensive)Exams are only offered at the announced time.

Missed exams result in zero score.

• Programming Projects• Exercises

• Please read the syllabus for late policy

CS 3214 Fall 2010

Grading• Tentative breakdown (subject to change):

– 12.5% Midterm– 22.5% Final– 42.5% Projects– 22.5% Exercises

• Not grading on standard scale; grade will be based on a curve of students attempting this course:– Median will divide B- and B– Grading on a curve means every assignment is important, doing

“just enough” is a strategy bound to result in a low grade– Calibrated not just by students in this cohort, but also past

offerings• Additional stipulations to pass the class

(aka “Auto-Fail Rules”)– Minimum Requirements must be met for each project– Necessary, not sufficient conditions

CS 3214 Fall 2010

Group Projects

• Projects are group projects• Working in a group more closely resembles what

you do outside of academia– Can design together, code together

• Group members must contribute equally• 2 students per group• Can change group, but only between projects• Exercises are done individually

CS 3214 Fall 2010

Forum Rules (aka Lex skottie)

• Not allowed:– Posting of any code that is part of your solution to the forum (*)– Posting the answers to design document or exercise questions– Posting detailed descriptions of your group’s design– Uncivil behavior

• (*) Exception: “1-line-rule”– Can post 1 line iff it causes a compile-time error

• You are encouraged to post:– Backtraces, debugging output, debugger messages– Illustrating example for a technique– Questions & explanations relating to concept– Questions & answers relating to projects in general– Pointers to external resources you have found

• If in doubt, ask before posting!

CS 3214 Fall 2010

Honor Code

• Will be strictly enforced in this class– Will not give warning or engage in discussions before filing

honor code cases where I believe they are warranted• Do not cheat

– Observe collaboration policy outlined in syllabus• Will use MOSS for software cheating detection

– Do not borrow code from other offerings– Follow collaboration policy

• Read all policies posted on the website– “I was not aware…” is no excuse

• If in doubt, ask!Cheating = Copying From Someone Else

+ Misrepresenting Work As Your Own

CS 3214 Fall 2010

Acknowledgements

• To avoid plagiarism, document (“acknowledge”) your sources

• Will draw in lectures from– Textbook– And other texts, in particular Silberschatz et al’s book

(“Dinosaur book”); Stalling’s book and Tannenbaum’s Modern Operating Systems

– Course material created for other courses– And other sources as appropriate

CS 3214 Fall 2010

Prerequisites

• Knowledge of computer organization (CS 2506)• Knowledge of algorithms & data structures (CS

2114)

• Please submit prerequisite form

• Some knowledge of C

CS 3214 Fall 2010

Talking about C…

#define offsetof(TYPE, MEMBER) \((size_t) &((TYPE *) 0)->MEMBER)

struct point { int x; int y; int z; char c; float o;};Q.: What is offsetof(struct point, y)? offsetof(struct point, o)?

#define offsetof(TYPE, MEMBER) \((size_t) &((TYPE *) 0)->MEMBER)

struct point { int x; int y; int z; char c; float o;};Q.: What is offsetof(struct point, y)? offsetof(struct point, o)?

0: x (4 byte int)

8: z (4 byte int)12: c (1 byte char)

4: y (4 byte int)

16: o (4 byte float)13: 3 byte padding

CS 3214 Fall 2010

Role of this Course

• Dual role:– Core requirement

• What should every student know about systems?

– Preparation for senior-level OS/networking course in Spring

• Capstone course for students choosing the Systems & Networking track: design an OS

• Perspective taken is that of a programmer using a system, not of a designer building one

Outcomes

• Be productive in using an OS – focus on Unix here

• Understand execution and optimization

• Understand overall architecture and concepts

• Understand interaction between apps and OS

• Understand concepts underlying threading, scheduling, virtual memory, networking, and virtualization

CS 3214 Fall 2010

Topic 0: Unix

• Throughout: we will be using Linux

• You are expected to already bring, or quickly pick up, the necessary skills– Will not set class time aside for this, but am

happy to discuss questions on the forum

• Exercise 1 may help

CS 3214 Fall 2010

Topic 1: Programs and Data

• Understand how programs are built, how they execute– Role of the compiler, assembler, and linker

• Learn to read and understand x86 code• Learn how to use a debugger• Understand security implications• Assume knowledge of bytes & bits as provided in

CS250X• Projects:

– “Binary Bomb”– “Buffer Bomb”

CS 3214 Fall 2010

Topic 2: Performance

• Learn– how to optimize code– how not to optimize code– how to measure performance– the impact of memory hierarchies

CS 3214 Fall 2010

Topic 3: Processes and Threads

• Learn the underlying abstractions

• Learn how to use them

• Subtopics:– System calls and exceptions– Thread and process APIs– Interprocess Communication

• Project:– Write your own shell

CS 3214 Fall 2010

Topic 4: Concurrency & Synchronization

• Learn about race conditions

• Learn commonly used synchronization techniques in C and Java

• Learn how to manage concurrency

• Understand deadlock and how to prevent it

CS 3214 Fall 2010

Topic 5: Memory

• Understand user-level memory management– Explicit vs. automated– User-level APIs for shared memory

• Understand concepts underlying Virtual Memory

• Understand impact on programmer– Memory tools

• Project:– User-level malloc()

CS 3214 Fall 2010

Topic 6: I/O and Networking

• Understand I/O facilities and layers• Understand use of socket API and

underlying abstractions, and basic protocol design with a focus on HTTP

• Understand how to write multi-threaded and event-based programs

• Project:– A multi-threaded HTTP server

CS 3214 Fall 2010

Topic 7: Virtualization

• Understand underlying concepts

• Understand resource management

• Exercise:– Set up your own hosted VM in Amazon cloud

(AWS)

CS 3214 Fall 2010