1. CS 162 Discussion Section Week 7

2. Recap What is demand paging?

3. Recap Why do we need demand paging?

4. Recap What does an OS do on a Page Fault?

5. Recap Page Replacement Policies FIFO, MIN, LRU …

6. Why is LRU not used in practice?

7. How does Clock replacement work?

8. Clock Replacement Illustration Max page table size 4 Invariant: point at oldest page –Page B arrives B u:0

9. Clock Replacement Illustration Max page table size 4 Invariant: point at oldest page –Page B arrives –Page A arrives –Access page A B u:0 A u:0

10. Clock Replacement Illustration Max page table size 4 Invariant: point at oldest page –Page B arrives –Page A arrives –Access page A –Page D arrives B u:0 A u:1 D u:0

11. Clock Replacement Illustration Max page table size 4 Invariant: point at oldest page –Page B arrives –Page A arrives –Access page A –Page D arrives –Page C arrives B u:0 A u:1 D u:0 C u:0

12. B u:0 Clock Replacement Illustration Max page table size 4 Invariant: point at oldest page –Page B arrives –Page A arrives –Access page A –Page D arrives –Page C arrives –Page F arrives F u:0 A u:1 D u:0 C u:0

13. E u:0 Max page table size 4 Invariant: point at oldest page –Page B arrives –Page A arrives –Access page A –Page D arrives –Page C arrives –Page F arrives –Access page D –Page E arrives A u:1 A u:0 D u:1 D u:0 Clock Replacement Illustration F u:0

14. Stop Hammer Time! Worksheet

15. Availability vs. Durability vs. Reliability

16. Rings of Protection [Introduced in MULTICS] http://en.wikipedia.org/wiki/File:Priv_rings.svg

17. Enter Virtualization Not Used Guest OS Xen

18. When to interrupt and when to poll?