We will examine how replacement policies impact miss rate. Assume a following 2-

Question

We will examine how replacement policies impact miss rate. Assume a following 2-way set associative cache. Consider the following block address sequence: 0, 1, 5, 2, 4, 8, 12, 16, 20, 24, 28, 0 0 address will fill left side of set0. 1 address will fill left side of set1. 5 address will fill right side of set1. 2 address will fill left side of set2. Assuming an LRU (least recently used) replacement policy, how many hits does this address sequence exhibit? Assuming an MRU (most recently used) replacement policy, how many hits does this address sequence exhibit?

Explanation / Answer

0,1,5,2,4,8,12,16,20,24,28,0

a) Assuming an LRU replacement polocy

Addr   POS

0 => set0, left

1 => set1, left

5 => set1, right

2 => set2, left

4 => set0, right

8 => set0, left (replace 0)

12 => set0, roght (replace 4)

16=> set0, left (replace 8)

20 => set0, right (replace 12)

24=> set0, left (replace 16)

28 => set0 right(replace 20)

0 => set0, left (replace 24)

Number of hits = 0

a) Assuming an MRU replacement polocy

  Addr   POS

0 => set0, left

1 => set1, left

5 => set1, right

2 => set2, left

4 => set0, right

8 => set0, right(replace 4)

12 => set0, roght (replace 8)

16=> set0, right (replace 12)

20 => set0, right (replace 16)

24=> set0, right (replace 20)

28 => set0 right(replace 24)

0 => hit

Number of hits = 1

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