Lecture1

Fred Kuhns ( ) CS523S: Operating Systems

CS523Operating Systems

Fred Kuhns

Applied Research Laboratory

Computer Science

Washington University


CS523 - Operating Systems

• Instructor: Fred Kuhns

• Phone: 935-6598

• Email: [email protected]

• Office Hours:Tu/Th: 4:00 - 5:00PM

• Location: TBD

• Class times: Tu/Th: 2:30 - 4:00PM


Course Materials

• Textbook: Real-Time Systems, Jane W. S. Liu

• Selected papers from the literature,

• Class handouts and presentation material,

• Class web page,

• OS man pages and web accessible documentation,

• UNIX account.


Programming Projects

• 3 projects plus a final project

• Final project: team/individual class presentations address a system issue covered in class. May build

on class projects. Report or implementation.

• Project focus: Correct, predictable behavior (of implementation) Performance (efficient execution) Completeness of design (address all issues) "readability" of code (can I understand it)


Exams, Homework and Grading

• Weekly: Homework assignment or Quiz

• Final Exam (no mid-term): Comprehensive

• Relative weights:25% Final exam20% Quizzes10% Homework30% Programming projects (10% per project)15% Final Project


Course OverviewOverview of OS design issues

o Review of general purpose OS serviceso Intro to Advanced OS Topics:

• Real-Time, Database, Distributed and Multi-processor

Detailed analysis of conventional OS internals:o Focus on UNIX - Linux, BSD, SVR4 and Macho Single/Multi-processoro Resource management

Focus on Real-Time: design and implementationo Performance and predictability issueso Resource scheduling and managing concurrency


Introduction

• Functions of an Operating SystemResource managementUser environment

• Design ApproachesLayered, Kernel and Virtual

• Types of Advanced Operating SystemsDistributed, Multiprocessor, Database and Real-time

• Overview of UNIX (why do we care)


Functions of an OS

• Resource ManagementTime management - temporal properties

CPU and disk transfer scheduling

Space management main and secondary storage allocation

Synchronization and deadlock handlingc

Accounting and status informations


Functions of an OS (cont)• User Environment - OS layer transforms bare

hardware machine into higher level abstractionsExecution environment - process management, file

manipulation, interrupt handling, I/O operations, language.

Error detection and handlingProtection and securityFault tolerance and failure recovery


Design Approaches• Deal with complexities of modern systems• Separation of Policies and Mechanisms

Policies - What should be doneMechanisms - How it should be doneLevin, R., E. Cohen, W. Corwin, F. Pollack and W. Wulf,

"Policy/Mechanism Separation in HYDRA," Proceedings of the 5th Symposium on Principles of Operating Systems, 1975, pp. 132-140.

• Three common approaches:Layered ApproachKernel ApproachVirtual Machine Approach


Layered Approach

Level Name Objects Example13 Shell User programming env. Bash statements12 User process User process Quit,kill,suspend,resume11 Directories Directories Create,destroy,attach,list10 Devices External: printer,display Create,open,close9 File system Files Create,open,close8 Communications Pipes Crreate,open,close7 Virtual memory Segments,pages Read,write,fetch6 Local secondary store Blocks,channel Read,write,fetch5 Primitive process Process,semaphore Suspend,resume,wait4 Interrupts Interrupt-handlers Invoke,mask,retry3 Procedures Procedure,stack,display Mark stack,call,return2 Instruction set Evaluation stack Load,store,add1 Electronic circuit Registers,gates,buses Clear,transfer,activate

Simplifies design, implementation and testingModular by dividing OS into functional layers.

HW

reso

urce

envi

ronm

ent


Kernel Based Approach

Kernel contains a collection of primitives which are used to build the OS

OS implements policyKernel implements mechanisms

Hardware

kernel

Operating system


Virtual Machine Approach

Virtual software layer over hardwareIllusion of multiple instances of hardwareSupports multiple instances of OSs

Hardware

Virtual machine software

VM1 VM2 VM3 VM4


• Layered:Dijkstra, E. W., "The Structure of THE Multiprogramming

System", Communications of the ACM, May 1968, pp. 341-346.• Layered (Ring):

Organick, E., The Multics System, MIT Press, Cambridge, MA. 1972.

• KernelBrinch Hansen, P., "The Nucleus of a Multiprogramming

System", Communications of the ACM, Apr. 1970, pp. 238-241.Wulf, W., E. Cohen, W. Corwin, A. Jones, R. Levin, C. Pierson,

and F. Pollack, "HYDRA: The Kernel of a Multiprocessor Operating System", Communications of the ACM, June 1974, pp. 337-345.

• VirtualSeawright, L., and R. MacKinnon, "VM/370 - A Study of

Multiplicity and Usefulness", IBM Systems Journal, 1979, pp. 4-17.


Types of Advanced OSs

Distributed Operating SystemsMultiprocessor Operating SystemsDatabase Operating SystemsReal-time Operating Systems


Distributed Operating Systems

• Controls and manages resources for a network of autonomous computersmanage both hardware and software resources behaves as a single monolithic system.

• User not aware of program or resource location• Design issues same as traditional systems• Practical issues:

lack of shared memory lack of global clockunpredictable communication delays.


Multiprocessor Operating Systems• Consists of a set of processors that

share a set of physical memory blocksshare a common clock "share" over an interconnection network.

• Control and manage resources hardware and software resourcesviewed as a uniprocessor system.

• Design issues same as traditional system.• Practical issues:

increased complexity of synchronization, scheduling, memory management, protection and security.


Database Operating Systems• Database systems place increased demands on an

operating system to efficiently support: concept of a transactionsmanage large volumes of dataconcurrency controlsystem failure control


Real-time Operating Systems

• Place application specific special requirements on an operating system.

• Policies and mechanisms are geared to ensuring jobs meet their deadlines.

• Problem is one of resource scheduling and overall system utilization.


Why UNIX• Historical significance

• Advanced features developed for or ported to UNIX

• Availability of source code and research papers

• Importance to present and future research activities at WashU

• Highlights key design and architectural issues


Traditional UNIX kernel

• Bloated kernel• Inflexible: supported single type of

file system,process schedulingexecutable file format

file system

virtual memory

loader

block dev char dev

kernel


Modern UNIX

• Separation of policy and mechanism

• modular design and implementation (layered)

Acrobat Document


References

• Original UNIX implementation:D. M. Ritchie, and K. Thompson, “The UNIX

Time-Sharing System”, Communications of the ACM, Vol. 17, No. 7, Jul. 1974, pp. 365-375.

Lecture1

Technology

realtime systems

operating systems controls

systems fred kuhns

ibm systems journal

mechanisms hardware

resources hardware

memory management

advanced os topics