chapter 22 - beyond physical memory policies

Question 1

How is RAM treated in the context of paging?

Answer 1

As a cache for virtual memory stored on disk

Question 2

What is the formula for Average Memory Access Time (AMAT)?

Answer 2

AMAT = T(M) + P(miss) × T(D)

T(M): Memory access time
T(D): Disk access time
P(miss): Page miss rate

Question 3

What is Belady’s MIN policy?

Answer 3

Evict the page that won’t be used for the longest time in the future

Question 4

Why is Belady’s algorithm not used in real systems?

Answer 4

It requires future knowledge of memory accesses

Question 5

What is FIFO (First-In, First-Out) replacement?

Answer 5

Evict the page that was loaded earliest, regardless of usage

Question 6

What is a downside of FIFO?

Answer 6

It may evict heavily-used pages just because they’re old

Question 7

What is Random Replacement?

Answer 7

Evict a random page

Question 8

What is LRU (Least Recently Used)?

Answer 8

Evict the page that has not been used in the longest time