COSC1078 Introduction to Information Technology Lecture 17 Memory and Deadlock

Lecture 17: Operating Systems Intro to IT

COSC1078 Introduction to Information Technology

Lecture 17

Memory and DeadlockJames Harland

james.harland@rmit.edu.au

Lecture 17: Memory & Deadlock Intro to IT

Introduction

James Harland• Email: james.harland@rmit.edu.au• URL: www.cs.rmit.edu.au/~jah• Phone: 9925 2045• Office: 14.10.1 • Consultation: Mon 4.30-5.30, • Thu 11.30-12.30What colour is my office

door? Carpet? Chair?

Lecture 17: Memory and Deadlock Intro to IT

Introduction to IT1 Introduction 2 Images3 Audio4 Video WebLearnTest 1 5 Binary Representation Assignment 16 Data Storage7 Machine Processing8 Operating Systems WebLearn Test 29 Processes Assignment 210 Internet11 Internet Security   WebLearn Test 312 Future of IT Assignment 3, Peer and Self Assessment

Lecture 17: Memory and Deadlock Intro to IT

Overview Questions?

Assignments 2 & 3

Peer and Self Assessment

Memory and Deadlock

Questions?

Lecture 17: Review Intro to IT

Assignments 2&3

Assignment 2: Due this week ()No single`right’ answerMain issue is to justify options to Granny

Assignment 3: start thinking about research topic

Lecture 17: Memory and Deadlock SE Fundamentals

Tutorials Held each week Classes of up to 24 Tutor will answer questions related to materials Good place for individual feedback Peer and self assessment Peer learning groups (5 or 6) Assessed on process, not product Assessed in last tutorial Trial assessments in weeks 4 and 8

Lecture 17: Memory and Deadlock SE Fundamentals

Self and Peer Assessment How well has each person contributed to the

group? Evaluated over the entire semester Assessed on process, not product Work out a grade for each person (CR, DI etc) Then convert this to a mark out of 20 Submit list of marks to tutor with justifications Repeat previous step until the tutor is satisfied See guidelines in Blackboard material

Lecture 17: Memory and Deadlock Intro to IT

Processes Executing in Context

Program Counter

InstructionRegister

CC ROMRAM

Processor Memory Disk00

BBCC

Lecture 17: Memory and Deadlock Intro to IT

Processes Executing in Context

Program Counter

InstructionRegister

BB ROMRAM

Processor Memory Disk00

BB

Lecture 17: Memory and Deadlock Intro to IT

Processes Executing in Context

Program Counter

InstructionRegister

FF ROMRAM

Processor Memory Disk00

FF

Lecture 17: Memory and Deadlock Intro to IT

Processes Executing in Context

Program Counter

InstructionRegister

BB ROMRAM

Processor Memory Disk00

BB

Lecture 17: Memory and Deadlock Intro to IT

``Thomas, you wouldn’t! Naughty!’’

Program Counter

InstructionRegister

BB ROMRAM

Processor Memory Disk00

BB

Lecture 17: Memory and Deadlock Intro to IT

``Thomas, you wouldn’t! Naughty!’’

Program Counter

InstructionRegister

BB ROMRAM

Processor Memory Disk00

BB

Lecture 17: Memory and Deadlock Intro to IT

``Thomas, you wouldn’t! Naughty!’’

Program Counter

InstructionRegister

BB ROMRAM

Processor Memory Disk00

BB

Lecture 17: Memory and Deadlock Intro to IT

Software `Programs should be able to do anything!’ (???)

Programs should be able to do anything reasonable

What is reasonable?

Not changing OS, not deleting other processes from memory, not playing with other people’s things, …

Lecture 17: Memory and Deadlock Intro to IT

Memory Management

Memory Disk

Mine!

Mine!

Mine!

STOP IT!

Lecture 17: Memory and Deadlock Intro to IT

Memory Management

Memory DiskHMM ...

sandbox

Lecture 17: Memory and Deadlock Intro to IT

Virtual Memory

What if memory requirements exceed memory size?

Pretend we have more!

Shuffle required parts (pages) between disk and memory

Not every memory cell is needed all the time…

Lecture 17: Memory and Deadlock Intro to IT

Virtual MemoryVirtual Memory

DiskPhysical MemoryP

rocesssor

Lecture 17: Memory and Deadlock Intro to IT

Co-ordination and locking

MINE!

MINE!

MINE!

Works fine for one resource …

Lecture 17: Memory and Deadlock Intro to IT

Deadlock

Deadlock: neither can get both resources

BORING!

Lecture 17: Memory and Deadlock Intro to IT

Deadlock requirements

Deadlock requires:

1. Competition for nonshareable resources2. Processes request multiple resources

sequentially3. Resources cannot be forcibly retrieved

Avoid deadlock by preventing 1 or 2Detect and correct deadlock by falsifying 3

Lecture 17: Memory and Deadlock Intro to IT

Deadlock avoidance

Spooling makes nonshareable resources look like shareable ones …

Lecture 17: Memory and Deadlock Intro to IT

Operating Systems

Highly complex software systems

30-40 million lines of code

Lots of processes associated with them

Probably most sophisticated software ever written

Not many of them around …

Lecture 17: Memory and Deadlock Intro to IT

Operating Systems

Lecture 16: Processes Intro to IT

Conclusion

Work on Assignment 2 (and 3?)

Research Topic for Assignment 3

Finish reading book!