Transcript General • Pseudo LRU (PLRU) records a partial order, using 3 bits per-set: – Bit0 specifies whether LRU way is either one of.

General
• Pseudo LRU (PLRU) records a partial order, using 3 bits
per-set:
– Bit0 specifies whether LRU way is either one of 0 and 1 or one of
2 and 3.
– Bit1 specifies which of ways 0 and 1 was least recently used
– Bit2 specifies which of ways 2 and 3 was least recently used
bit1
bit0
0
1
0
1
0
0
1
2
1 bit2
3
Example
• Suppose a sequence
of 3,2,1,0
• The plru at that point
is 111
• Now suppose we
access #3, so it will
become the MRU.
– We can choose 2 as
LRU 111 110
– We can choose 1 to
LRU. 111  010
bit0
0
1
0
1
0
bit1
1 bit2
MRU
0
bit1
1
2
3
bit0
0
1
0
1
0
0
1
LRU
2
LRU
1 bit2
3
MRU