1. Lecture 17: Operating Systems Intro to IT COSC1078 Introduction to Information Technology Lecture 17 Memory and Deadlock James Harland james.harland@rmit.edu.au

2. Lecture 17: Memory & DeadlockIntro 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 11.30-12.30 What colour is my office door? Carpet? Chair?

3. Lecture 17: Memory and DeadlockIntro 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 ITAssignment 3, Peer and Self Assessment

4. Lecture 17: Memory and DeadlockIntro to IT Overview  Questions?  Assignments 2 & 3  Peer and Self Assessment  Memory and Deadlock  Questions?

5. Lecture 17: ReviewIntro 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

6. Lecture 17: Memory and DeadlockSE 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

7. Lecture 17: Memory and DeadlockSE 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

8. Lecture 17: Memory and DeadlockIntro to IT Processes Executing in Context Program Counter Instruction Register CC ROM RAM Processor Memory Disk 00 BB CC

9. Lecture 17: Memory and DeadlockIntro to IT Processes Executing in Context Program Counter Instruction Register BB ROM RAM Processor Memory Disk 00 BB

10. Lecture 17: Memory and DeadlockIntro to IT Processes Executing in Context Program Counter Instruction Register FF ROM RAM Processor Memory Disk 00 FF

11. Lecture 17: Memory and DeadlockIntro to IT Processes Executing in Context Program Counter Instruction Register BB ROM RAM Processor Memory Disk 00 BB

12. Lecture 17: Memory and DeadlockIntro to IT ``Thomas, you wouldn’t! Naughty!’’ Program Counter Instruction Register BB ROM RAM Processor Memory Disk 00 BB

13. Lecture 17: Memory and DeadlockIntro to IT ``Thomas, you wouldn’t! Naughty!’’ Program Counter Instruction Register BB ROM RAM Processor Memory Disk 00 BB

14. Lecture 17: Memory and DeadlockIntro to IT ``Thomas, you wouldn’t! Naughty!’’ Program Counter Instruction Register BB ROM RAM Processor Memory Disk 00 BB

15. Lecture 17: Memory and DeadlockIntro 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, …

16. Lecture 17: Memory and DeadlockIntro to IT Memory Management Memory Disk Mine! STOP IT!

17. Lecture 17: Memory and DeadlockIntro to IT Memory Management Memory Disk HMM... sandbox

18. Lecture 17: Memory and DeadlockIntro 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…

19. Lecture 17: Memory and DeadlockIntro to IT Virtual Memory DiskPhysical Memory ProcesssorProcesssor

20. Lecture 17: Memory and DeadlockIntro to IT Co-ordination and locking MINE! Works fine for one resource …

21. Lecture 17: Memory and DeadlockIntro to IT Deadlock Deadlock: neither can get both resources BORING!

22. Lecture 17: Memory and DeadlockIntro to IT Deadlock requirements Deadlock requires: 1.Competition for nonshareable resources 2.Processes request multiple resources sequentially 3.Resources cannot be forcibly retrieved Avoid deadlock by preventing 1 or 2 Detect and correct deadlock by falsifying 3

23. Lecture 17: Memory and DeadlockIntro to IT Deadlock avoidance Spooling makes nonshareable resources look like shareable ones …

24. Lecture 17: Memory and DeadlockIntro 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 …

25. Lecture 17: Memory and DeadlockIntro to IT Operating Systems

26. Lecture 16: ProcessesIntro to IT Conclusion  Work on Assignment 2 (and 3?)  Research Topic for Assignment 3  Finish reading book!