Fully Associative Cache Memory Budgeted by Access Type
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Solution Overview
Problem
Conventional cache memory systems lack an efficient mechanism to dynamically allocate storage elements based on memory access types, leading to suboptimal performance due to inadequate consideration of memory access patterns.
Innovation Solution
A fully associative cache memory system that allocates storage elements based on memory access types (MATs) using counters and thresholds to manage allocation and replacement, ensuring efficient allocation by mapping MATs into subsets and employing heterogeneous replacement policies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional cache memory systems use uniform allocation policies for all memory accesses, then the cache structure is simple and easy to implement, but cache performance is suboptimal due to inadequate consideration of different memory access patterns
Solution Approach 1:
The patent segments the cache allocation mechanism by introducing separate counters and thresholds for different memory access types (MATs). Each MAT has its own allocation policy parameters, allowing differentiated treatment of various access patterns while maintaining the overall cache structure. This segmentation enables optimized allocation for each access type without requiring complete restructuring of the cache system.
Solution Approach 2:
The patent implements dynamic allocation policies where the allocation unit can adjust which storage elements receive new data based on current cache state, MAT thresholds, and replacement policies. The system dynamically selects between allocation into any valid storage element or replacement of specific elements based on MAT-specific criteria, making the allocation mechanism adaptive rather than static.
2Productivity
If the cache memory allocates storage elements for all memory access types equally, then the implementation is straightforward, but the cache efficiency is reduced due to lack of optimization for specific access patterns
Solution Approach 1:
The patent divides the cache management into segmented components: separate counters for each MAT, separate thresholds for each MAT, and MAT-specific allocation logic. This segmentation allows efficient management of each access type independently while avoiding the need for complex global management schemes. Each MAT's counter and threshold pair forms a self-contained management unit.
Solution Approach 2:
The patent changes the parameters of the allocation mechanism by introducing MAT-specific counters and thresholds as controllable parameters. These parameters can be adjusted to optimize performance for different access patterns. The allocation efficiency is improved by allowing these parameters to vary based on MAT rather than being fixed uniform values.
3Productivity
If the cache memory replaces storage elements without considering memory access types, then the replacement policy is simple, but the hit rate decreases due to suboptimal replacement decisions
Solution Approach 1:
The patent segments the replacement policy by MAT, where each memory access type has its own replacement criteria based on MAT-specific counters and thresholds. This allows the system to make replacement decisions optimized for each access type rather than using a single generic policy, improving hit rates through targeted replacement strategies.
Solution Approach 2:
The patent implements feedback mechanisms where counters track the number of valid storage elements for each MAT, and thresholds provide feedback boundaries for replacement decisions. The allocation unit continuously monitors these counters and compares them against thresholds to determine when replacement should occur, creating a feedback-driven replacement policy that adapts to cache state.
Data Source
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AI summary
A fully associative cache memory, comprising: an array of storage elements; an allocation unit that allocates the storage elements in response to memory accesses that miss in the cache memory. Each memory access has an associated memory access type (MAT) of a plurality of predetermined MATs. Each valid storage element of the array has an associated MAT. For each MAT, the allocation unit maintains: a counter that counts of a number of valid storage elements associated with the MAT; and a corresponding threshold. The allocation unit allocates into any of the storage elements in response to a memory access that misses in the cache, unless the counter of the MAT of the memory access has reached the corresponding threshold, in which case the allocation unit replaces one of the valid storage elements associated with the MAT of the memory access.