L1 Cache Controller Memory Attribute Sharing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In prior art devices, memory attribute registers are not visible in the level one data cache controller, preventing performance optimizations such as merge writes for external addresses based on cacheability and optimizing cache state machines, and requiring the level one data cache controller to generate and send victims for read accesses to non-cacheable external addresses.
Innovation Solution
The level one memory controller maintains a local copy of the cacheability bit of each memory attribute register, allowing it to optimize memory system performance by merging writes for external addresses, optimizing cache state machines based on cacheability, and avoiding the generation and transmission of victims for read accesses to non-cacheable addresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If memory attribute registers are not visible in the level one data cache controller, then the device complexity is reduced, but the productivity of the memory system deteriorates due to inability to perform merge writes and optimize cache operations
Solution Approach 1:
The patent divides the memory controller functionality into two segments: the level two memory controller maintains the master copy of memory attribute registers, while the level one data cache controller maintains a local copy specifically for optimization purposes. This segmentation allows the level one controller to access cacheability information without requiring full visibility of all memory attribute registers, thus improving performance while controlling complexity.
Solution Approach 2:
The level one data cache controller creates a local copy of the cacheability bits from the memory attribute registers. This copy enables the controller to make optimization decisions (merge writes, optimize state machines, avoid victim generation) without directly accessing or managing the full memory attribute register structure, resolving the contradiction between performance and complexity.
2Productivity
If the level one data cache controller generates and sends victims for read accesses to non-cacheable external addresses, then the reliability of cache coherence is improved, but the productivity of the memory system deteriorates due to unnecessary operations
Solution Approach 1:
The level one data cache controller performs preliminary action by checking the local copy of cacheability bits before generating victim entries. This advance knowledge allows the controller to determine that certain read accesses to non-cacheable addresses will not benefit from caching, thereby avoiding unnecessary victim generation and transmission operations while maintaining cache coherence reliability.
Solution Approach 2:
The patent extracts the cacheability determination logic from the general cache control flow by using the local copy of memory attribute registers. This extraction allows the controller to bypass victim generation for non-cacheable addresses, removing unnecessary operations while preserving the reliability mechanism for actually cacheable addresses.
3Productivity
If merge writes are not performed for external addresses, then the device complexity is reduced, but the productivity deteriorates due to inability to optimize write operations based on cacheability
Solution Approach 1:
The level one data cache controller uses its local copy of cacheability bits to determine whether to perform merge writes for external addresses. This copy provides the necessary information to implement write optimization logic without requiring complex interactions with the level two controller or direct access to the full memory attribute register structure, thus improving write efficiency while controlling complexity.
Solution Approach 2:
The patent applies local quality by giving the level one data cache controller a localized view of cacheability information through its local copy. This localized information enables the controller to make write merging decisions specific to its operational context without requiring global visibility of all memory attributes, optimizing write operations with controlled complexity.
Data Source
AI summary
The level one memory controller maintains a local copy of the cacheability bit of each memory attribute register. The level two memory controller is the initiator of all configuration read/write requests from the CPU. Whenever a configuration write is made to a memory attribute register, the level one memory controller updates its local copy of the memory attribute register.