Final ReviewCS-502 Fall 2006 1

CS-502 Operating Systems Fall 2006

Review

Final ReviewCS-502 Fall 2006 2

Week 1

• Concurrency• Processes – a fundamental abstraction

• Interrupts, dispatching, ready queue

• Busy waiting, Peterson’s solution

• Critical sections, semaphores

• Processes (à la Unix, Linux, Windows)• What does this include?

• Process states

• fork() and exec()

Final ReviewCS-502 Fall 2006 3

Week 2

• Threads• Concurrency within an address space

• Shared (virtual) memory programming

• Lightweight concurrency

• Scheduling• Goals and criteria

• FCFS, RR, Priority, SJF, etc.

• Multi-level scheduling

• (later) Rate monotonic, Earliest Deadline First– (for real time problems)

Final ReviewCS-502 Fall 2006 4

Week 3

• Producer-consumer models• Interprocess communication

• Shared memory• Semaphores• Software interrupts & signals to processes• Pipes• Message passing

• Monitors• Remote procedure call

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Week 4 – Memory Management

• Partitioning physical memory

• Base and Limit registers• The first “virtual” memory

• Easy relocation

• Segmentation• Multiple segments

• Paging• Page tables & page translation

• Copy-on-write & other tricks

Final ReviewCS-502 Fall 2006 6

Week 4 – Memory Management (cont.)

• Virtual Memory• Page replacement algorithms

• Paging performance calculations

• Locality of reference ; thrashing

• Cache: • Fundamental principle that cuts across all of computing

• Physical memory is cache of virtual memory

• TLB is a cache of page tables

• File caches, activity caches, etc.

• Fundamental issues in caching

Final ReviewCS-502 Fall 2006 7

Week 5 – I/O subsystems

• Types of I/O devices• Character vs. block vs. graphic vs. streaming

• Types of transfers• Programmed I/O

• Interrupt-driven

• DMA

• Device drivers• Statically loaded vs. dynamically loaded

• Interrupt handling: bottom vs. top half

Final ReviewCS-502 Fall 2006 8

Weeks 6 & 7 – Disks and File Systems

• Disks• I/O devices mostly used for storage within system• Randomly accessed; blocks independently writeable• Bad block management

• Disk economics• Moore’s law increase in densities• Slow, linear increase in performance

• RAID• Protection against disk failures• Some improvements in performance

• Stable storage• Also protection against failures• Generalizes to transaction management

Final ReviewCS-502 Fall 2006 9

Weeks 6 & 7 – Disks and File Systems (cont.)

• Disk scheduling algorithms• Not particularly relevant except in some database or

multimedia systems

• File:• Fundamental abstraction of persistent storage• Also used for system functions (including protection)

• File metadata• Information about the file, stored with file

• Container vs. contents

Final ReviewCS-502 Fall 2006 10

Weeks 6 & 7 – Disks and File Systems (cont.)

• Operations on files• Read, write, seek, create, delete, truncate, open, close, etc.

• Types of file allocation• Contiguous

• Linked (or FAT)

• Indexed

• Directory• A special kind of file

• Linux virtual file systems• Mounting

Final ReviewCS-502 Fall 2006 11

Week 8 – Networks

• OSI seven-layer stack• Connection

• A fundamental abstraction of networking

• Socket• An OS abstraction; one end of a connection

• Network layer• Routing

• Transport layer• Reliable transmission

Final ReviewCS-502 Fall 2006 12

Week 9 – Distributed File System

• DFS naming & access

• DFS caching

• File server semantics• Stateless vs. stateful

• Example systems• NFS – a stateless system

• AFS – very much a stateful system

Final ReviewCS-502 Fall 2006 13

Week 10 – Multiprocessing and Distributed Systems

• Types of multi-computers• Shared memory multiprocessors

• Clusters of separate computers

• Distributed systems

• SMP• One operating system

• Multiple computations in kernel at once

• Processes & interrupts execute on any processor

Final ReviewCS-502 Fall 2006 14

Week 10 – Multiprocessing and Distributed Systems (cont.)

• Clusters• Physically close; separate OS on each machine

• Shared I/O and disk devices

• Fast IPC & RPC

• Load balancing

• Distributed computing• Physically separated; internet communications

• Distributed file systems; NFS, etc.

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Week 11 – Virtualization

• Decoupling of hardware from {OS, appl.}

• Insulates systems from each other• Commissioning and updates

• Debugging new version

• Separate OS required by separate applications

• Dynamic repartitioning of hardware• Move running applications

• Balancing shifting loads

Final ReviewCS-502 Fall 2006 16

Week 11 & 12 – Multimedia Systems

• Delivery of audio, video, etc, streams to computers

• Broad impact in last decade• TiVo, iPod, video on demand, audio/video on PCs

• CD & DVD disk and file formats

• Compression is essential• JPEG, MPEG, MP-3

• Lossless vs. lossy

• Take advantage of temporal locality

Final ReviewCS-502 Fall 2006 17

Week 11 & 12 – Multimedia Systems (cont.)

• Processor and disk scheduling• Rate monotonic: equivalent to any static algorithm

• Earliest deadline first: equiv. to any dynamic alg.

• Multimedia file organization• Frame vs. blocked; Locations on disk

• Network streaming• Progressive download vs. real-time

• Real-time streaming• Live vs. video-audio on demand

Final ReviewCS-502 Fall 2006 18

Week 13 – Protection and Security

• Protection• Mechanisms in OS to keep processes from things they should

not touch

• Access control lists vs. capabilities

• Separate policy from mechanism

• Security• Validating credentials of users, processes

• Validating authenticity of messages, controls, etc.

• Cryptography• General security mechanism

• Public key vs. private key methods

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Term Projects

• At least 5 real-time operating systems• eCos, VxWorks, QNX Neutrino, Itron, ThreadX, Nucleus

• Lots of embedded systems• RTOS, plus Visual DSP++• Personal devices: PalmOS, Symbian• Games: PSP• Very small devices: TinyOS, BrickOS

• Big systems• Telephone exchanges: Chorus• Corporate computing: Open VMs

• Eclectic systems• Inferno, Squeak

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Other topics

• OS organization• Big vs. small

• Monolithic kernel vs. microkernel

• Linux kernel projects• Adding a system call

• Building a message passing subsystem

• Discovering answers to questions

• …

Final ReviewCS-502 Fall 2006 21

Questions