Lecture 5 - Directory Protocols-Flat Memory-Based Directories Notes

: Lecture 5 - Directory Protocols-Flat Memory-Based Directories Notes

 Page 1


1
Lecture 5: Directory Protocols
• Topics: directory-based cache coherence implementations
Page 2


1
Lecture 5: Directory Protocols
• Topics: directory-based cache coherence implementations
2
Flat Memory-Based Directories
Main memory
Cache 1 Cache 2 Cache 64
…
…
Block size = 128 B
Memory in each node = 1 GB
Cache in each node = 1 MB
For 64 nodes and 64-bit directory,
Directory size = 4 GB
For 64 nodes and 12-bit directory,
Directory size = 0.75 GB
Page 3


1
Lecture 5: Directory Protocols
• Topics: directory-based cache coherence implementations
2
Flat Memory-Based Directories
Main memory
Cache 1 Cache 2 Cache 64
…
…
Block size = 128 B
Memory in each node = 1 GB
Cache in each node = 1 MB
For 64 nodes and 64-bit directory,
Directory size = 4 GB
For 64 nodes and 12-bit directory,
Directory size = 0.75 GB
3
Flat Memory-Based Directories
L2 cache
L1 Cache 1 L1 Cache 2 L1 Cache 64
…
…
Block size = 64 B
L2 cache in each node = 1 MB
L1 Cache in each node = 64 KB
For 64 nodes and 64-bit directory,
Directory size = 8 MB
For 64 nodes and 12-bit directory,
Directory size = 1.5 MB
Page 4


1
Lecture 5: Directory Protocols
• Topics: directory-based cache coherence implementations
2
Flat Memory-Based Directories
Main memory
Cache 1 Cache 2 Cache 64
…
…
Block size = 128 B
Memory in each node = 1 GB
Cache in each node = 1 MB
For 64 nodes and 64-bit directory,
Directory size = 4 GB
For 64 nodes and 12-bit directory,
Directory size = 0.75 GB
3
Flat Memory-Based Directories
L2 cache
L1 Cache 1 L1 Cache 2 L1 Cache 64
…
…
Block size = 64 B
L2 cache in each node = 1 MB
L1 Cache in each node = 64 KB
For 64 nodes and 64-bit directory,
Directory size = 8 MB
For 64 nodes and 12-bit directory,
Directory size = 1.5 MB
4
Flat Cache-Based Directories
Main memory
…
Block size = 128 B
Memory in each node = 1 GB
Cache in each node = 1 MB
6-bit storage in DRAM for each block;
DRAM overhead = 0.375 GB
12-bit storage in SRAM for each block;
SRAM overhead = 0.75 MB
Cache 7 Cache 3 Cache 26
Page 5


1
Lecture 5: Directory Protocols
• Topics: directory-based cache coherence implementations
2
Flat Memory-Based Directories
Main memory
Cache 1 Cache 2 Cache 64
…
…
Block size = 128 B
Memory in each node = 1 GB
Cache in each node = 1 MB
For 64 nodes and 64-bit directory,
Directory size = 4 GB
For 64 nodes and 12-bit directory,
Directory size = 0.75 GB
3
Flat Memory-Based Directories
L2 cache
L1 Cache 1 L1 Cache 2 L1 Cache 64
…
…
Block size = 64 B
L2 cache in each node = 1 MB
L1 Cache in each node = 64 KB
For 64 nodes and 64-bit directory,
Directory size = 8 MB
For 64 nodes and 12-bit directory,
Directory size = 1.5 MB
4
Flat Cache-Based Directories
Main memory
…
Block size = 128 B
Memory in each node = 1 GB
Cache in each node = 1 MB
6-bit storage in DRAM for each block;
DRAM overhead = 0.375 GB
12-bit storage in SRAM for each block;
SRAM overhead = 0.75 MB
Cache 7 Cache 3 Cache 26
5
Flat Cache-Based Directories
Main memory
…
6-bit storage in L2 for each block;
L2 overhead = 0.75 MB
12-bit storage in L1 for each block;
L1 overhead = 96 KB
Cache 7 Cache 3 Cache 26
Block size = 64 B
L2 cache in each node = 1 MB
L1 Cache in each node = 64 KB
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