In-class notes for 10/07/2020 (CS 273 (OS), Fall 2020)

______ In-class notes for 10/07/2020 (CS 273 (OS), Fall 2020)

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In-class notes for 10/07/2020

CS 273 (OS), Fall 2020

Exams returned

Memory management overview

Swapping.
- Hole management
Paging (virtual memory).
- Last time
  
  Exercise; Jamboard
- Page replacement algorithms
- Terms; virtual address translation
- Hardware assists: MMU; TLB
Exercise

Assume 6 page frames, two processes with pages A1, A2, ... and B1, B2, ...
How many page faults are needed for
```
A1    A2    A3    A4    A1    A2    A3    A4  
  \  /  \  /  \  /  \  /  \  /  \  /  \  /  \
   B1    B2    B1    B3    B1    B4    B1    B2
```
for FIFO? For NRU? Here, boldface indicates modification of a page.
Assume that any R/M bits start at 0 and are never reset to 0 during this sequence
- Answer for FIFO: 14 page faults for A1, B1, A2, B2, A3, A4, B3(replacing A1), A1(B1), B1(A2), A2(B2), B4(A3), A3(A4), A4(B3), B2(A1)
- Answer for NRU: 12 - A1, B1, A2, B2, A3, A4, B3(A1), A1(B2), B4(A3), A3(A4), A4(B3), B2(A3)

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