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Lecture 17: Operating Systems Intro to IT
COSC1078 Introduction to Information Technology
Lecture 17
Memory and DeadlockJames Harland
Lecture 17: Memory & Deadlock Intro to IT
Introduction
James Harland• Email: [email protected]• URL: www.cs.rmit.edu.au/~jah• Phone: 9925 2045• Office: 14.10.1 • Consultation: Mon 4.30-5.30, • Thu 11.30-12.30
What colour is my office door? Carpet? Chair?
Lecture 17: Memory and Deadlock Intro to IT
Introduction to IT
1 Introduction
2 Images
3 Audio
4 Video WebLearnTest 1
5 Binary Representation Assignment 1
6 Data Storage
7 Machine Processing
8 Operating Systems WebLearn Test 2
9 Processes Assignment 2
10 Internet
11 Internet Security WebLearn Test 3
12 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’ answer
Main 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 ROM
RAM
Processor Memory Disk
00
BB
CC
Lecture 17: Memory and Deadlock Intro to IT
Processes Executing in Context
Program Counter
InstructionRegister
BB ROM
RAM
Processor Memory Disk
00
BB
Lecture 17: Memory and Deadlock Intro to IT
Processes Executing in Context
Program Counter
InstructionRegister
FF ROM
RAM
Processor Memory Disk
00
FF
Lecture 17: Memory and Deadlock Intro to IT
Processes Executing in Context
Program Counter
InstructionRegister
BB ROM
RAM
Processor Memory Disk
00
BB
Lecture 17: Memory and Deadlock Intro to IT
``Thomas, you wouldn’t! Naughty!’’
Program Counter
InstructionRegister
BB ROM
RAM
Processor Memory Disk
00
BB
Lecture 17: Memory and Deadlock Intro to IT
``Thomas, you wouldn’t! Naughty!’’
Program Counter
InstructionRegister
BB ROM
RAM
Processor Memory Disk
00
BB
Lecture 17: Memory and Deadlock Intro to IT
``Thomas, you wouldn’t! Naughty!’’
Program Counter
InstructionRegister
BB ROM
RAM
Processor Memory Disk
00
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 Memory
Virtual 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!
