Introduction

Tom Kelliher, CS 325

Jan. 28, 2009

Administrivia

Announcements

Assignment

Read Chapter 1.

Outline

1. Syllabus.

2. A ``grand tour:'' OS and system views, structure, and operation.

Coming Up

Continued ``grand tour.''

Syllabus

1. Objectives:
   1. Study operating system design.

   2. Understand threads and concurrency: Banking example.

   3. Appreciate connections to other areas of computer science.

2. C refresher project.

3. Internet resources.

4. Linux internals project orientation.

5. Class preparation.

6. (Doubtful) Possibilities for Other topics: deadlock, distributed systems, security and protection.

A Grand Tour

The Main Thing

An OS's responsibilities boil down to managing:

OS As Interface

(Process = running program. Separate address spaces. Threads share an address space.)

1. Top-down view: virtual machine abstraction -- convenient ``user'' interface. Abstractions: files, applications. I/O devices integrated into filesystem.
2. Bottom-up view: management of real resources: CPU cycles, memory, disk space, device allocations.
3. Secondary concerns: efficiency, fairness.

Abstractions:

1. Multiprogramming, protection and security.

   Threads.

2. Virtual memory.
3. File systems.
4. Virtualization.

OS Components

1. Kernel. Static. Process/thread, memory, I/O management and access.

   Timers.

2. Daemons. Provide additional services.
3. System applications: compilers, linkers, loaders.
4. User applications: shells, windowing systems, browsers, editors, etc.

The ``Hello world'' program:

1. Compiled into assembly code.
2. Assembled in machine code.
3. Written to a file.
4. Loaded into memory.
5. Linked against system libraries.
6. Executes.
7. Makes supervisor calls to access I/O devices through OS.

Computing System Organization

1. CPU, memory, I/O devices block diagram.

   I/O device bandwidth/latency differences.

   Process execution within this context. Data/code locality: caches. VM. DMA.

2. Single CPU, multiple CPU chips, multiple cores, hyperthreading. (Phoenix: eight ``CPUs.'')

   Why can't we just turn up the clock?

   Efficiencies with multiple cores vs. multiple CPU chips.

   Programming consequences.

3. Process, do I/O, repeat model.

4. Memory hierarchy. Speed, density, cost, volatility.

5. I/O architecture. Abstract models, device drivers, devices. Plug'n'play/pray.

OS Structure

1. Multiprogramming.

   Mental memory model:

   

   Timesharing vs. batch.

   Short-term, long-term schedulers.

   Physical, virtual memory. Swapping.

2. Interrupt driven kernel operation.

   Dual (or more) CPU modes: user, kernel modes. Privileged operations and/or I/O spaces.

   Interrupts, traps. Hardware timers.

Tom Kelliher