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CS 162 Discussion Section Week 7. Recap What is demand paging?

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Presentation on theme: "CS 162 Discussion Section Week 7. Recap What is demand paging?"— Presentation transcript:

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]

17 Enter Virtualization Not Used Guest OS Xen

18 When to interrupt and when to poll?

19


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