Operating Systems CSE 411 Introduction and Overview Sept Lecture 1 Instructor: Bhuvan Urgaonkar

About Me Bhuvan Urgaonkar –Ph.D., Sept. 2005, Univ. of Mass. Amherst –Research areas Operating systems, Distributed systems, Computer networks –Office hours: Thu 5-7 PM, or by appointment –Office: 338D, IST Building – cse Welcome!

Administrative Stuff

Teaching Assistants Yuan Fang –Office hours: M AM, W PM, 346D – cse Arjun R. Nath –Office hours: Tue 5-7 PM – cse

Online Resources and Text-book Course Web page: – All material will be available via ANGEL –Please seek help from the TAs if needed Textbook –Operating Systems Concepts, 7th ed. Silberschatz, Galvin, and Gagne

Course Mailing List Via ANGEL –Use with care I will send a test , please respond to my address if you don’t receive it by Friday Welcome to write to me or the TAs –Make sure to include “411” in the subject

Grading Quizzes (approx. one per week): 15% Written home-works (5): 15% Projects (3): 35% Exams (3): 35% 90+: A, 75-89: (A, B], 65-74: (B, C], … –Subject to change; will not make it stricter –No relative grading - relax :)

Grading Projects will be done in groups of 2 –One group of size 3 will be allowed if needed –If your partner drops the course … 2 Exams, each on a different subset of the material; final exam comprehensive Late policy: –Strict deadlines for quizzes and home-works 20% per extra day for projects –Inform TAs well in advance if there is a real reason for a delay in project submission –Same for conflict exams

Grading Projects –50% grade on how functional your project is –The other 50% on your write-up and presentation We will give instructions on what we expect when we make the projects available Quizzes: –Online on ANGEL –Multiple-choice, mostly

Computing Resources Solaris or Linux accounts for projects me or the TAs if you don’t have an account or have any doubts/problems

Academic Honesty Do all assignments on your own –Quizzes, home-works, projects We will use software to compare project source codes –Both partners on each team are expected to know everything about each project

Assumed Background First course on algorithms and data structures Comfortable programming in C/C++ –Comfortable with a debugger like gdb Preliminary understanding of computer architecture –We will cover some basics in this course Talk to me if you have doubts Background quiz to be turned in by next Monday

Before We Begin … Some advice –Speak up in class, ask questions –Attend all classes Hint: Ideas concerning homeworks, exam questions, … –Do all assignments on your own! –Make good use of office hours –Bring printouts to class and take notes on them –Read text-book soon after class Sections to read will be made available on the Web site alongside lecture notes Even better: read before class and ask questions

Operating Systems: Introduction & Background

What is an Operating System (OS)? Literal meaning –Software that helps operate a computer Lack of consensus on the term operate Overloaded term –Software that runs on a computer when nothing else is running (e.g., right after it boots up => kernel) Very restrictive, what about dynamically loaded device drivers? –Windows = Any other OS + Windows Media Player + … Very inclusive, why not everything else in the world?

What is an OS There is no single truth here –Our OS somewhere between these extremes Definition using negation –Applications Moving the burden to defining an application :) –OS = all software minus applications Helps the applications use the computer Helps manage the resources of the computer

Why do we need an OS? Why not provide this functionality in hardware? –Why this separate piece of software?

A Little Bit of History

The Dark Ages (1940s - 60s) Hardware: expensive; humans: cheap Evolution of functionality –Single user –Batch processing –Overlap of I/O and computation –Multi-programming

1. Single User One user at a time on console Computer executes one function at a time –No overlap: computation & I/O User must be at console to debug Multiple users => inefficient use of machine

2. Batch Processing Execute multiple “jobs” in batch: –Load program –Run –Print results, dump machine state –Repeat Users submit jobs (on cards or tape) Human schedules jobs A program loads & runs jobs –The Operating System More efficient use of machine, complicates debugging

3. Overlap I/O and Computation Before: machine waits for I/O to complete New approach: more work by the OS –Allow CPU to execute while waiting –Add buffering Data fills “buffer” and then output –and interrupt handling I/O events trigger a signal (“interrupt”) More efficient use of machine, but still one job at a time

4. Multiprogramming Allow several programs to run at same time –Run one job until I/O –Run another job, etc. OS manages interaction between programs: –Which jobs to start –Protects program’s memory from others –Decides which to resume when CPU available

So what does an OS do? Two kinds of functionality –Management of computer resources Sharing CPU between tasks Memory management –Certain services to users Load programs, run them

OS Complexity Increased functionality & complexity First OS failures –Multics (GE & MIT): announced 1963, released 1969 –OS/360 released with 1000 known bugs Need to treat OS design scientifically Managing complexity becomes key to…

The Renaissance (1970s) Hardware: cheap; humans: expensive Users share system via terminals The UNIX era –Multics: army of programmers, six years –UNIX: three guys, two years “Shell”: composable commands No distinction between programs & data But: response time & thrashing

The Industrial Revolution (1980s) Hardware very cheap; humans expensive Widespread use of PCs –IBM PC: 1981, Macintosh: 1984 Simple OS (DOS, MacOS) –No multiprogramming, concurrency, memory protection, virtual memory, … –Later: networking, file-sharing, remote printing… –GUI added to OS (“WIMP”)

The Modern Era (1990s-now) Hardware cheap; processing demands increasing “Real” operating systems on PCs –NT (1991); Mac OS X; Linux Different modalities: –Parallel: Multiple processors, one machine –Distributed: Multiple networked processors –Real-time: Strict or loose deadlines –Sensor networks: Many small computers

OSes Today Active research area (so I like to believe!) –Top CS conferences, several distinguished researchers/groups –Intersects with theory/algos., software engg., architecture, distrib. comp. Major market presence –Microsoft, Apple, HP, … New environments, new devices –Web, P2P systems, Internet apps, sensor networks, mobile devices, multimedia, … New challenges –Distributed systems, heterogeneous devices, ubiquitous computing, utility computing, mobile computing, autonomic computing

Outline of this Course

Course Outline Resource Management (and some services an OS provides to programmers) –CPU management –Memory management –I/O management (emphasis: Disk) Cross-cutting design considerations and techniques –Quality-of-service/fairness, monitoring, accounting, caching, software design methodology, security and isolation Advanced topics –Distributed systems –Data centers, multi-media systems, real-time systems, virtual machines

Next Time Background on Computer Architecture