Security Tag Prefetch Circuitry for Non-Contiguous Metadata Access
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Solution Overview
Problem
Existing prefetching techniques in processors face challenges in accurately predicting memory access patterns, leading to inefficiencies such as cache misses, increased power consumption, and unnecessary evictions, while also requiring significant circuit area and power for prefetch control.
Innovation Solution
Implementing a Bayesian pattern engine (BPE) for program counter-based learning, compressed map storage for demoted access maps, adaptive adjustment of prefetch constraints, fuzzy pattern matching, and prefetching for security tag metadata to enhance prefetch accuracy and efficiency across multiple cache levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If prefetching is implemented to reduce memory latency, then cache hit rate improves, but power consumption and circuit area increase
Solution Approach 1:
The patent implements selective prefetching where only certain cache blocks are prefetched based on access pattern prediction, rather than prefetching all blocks. The system uses a prediction mechanism that determines which blocks to prefetch, avoiding unnecessary prefetch operations and reducing power consumption while maintaining improved cache hit rates for predicted accesses
2Reliability
If prefetching is implemented to reduce memory latency, then cache hit rate improves, but circuit area increases
Solution Approach 1:
The patent combines the prefetch control logic with existing cache control structures, merging prediction and prefetch functions into the cache management unit. This integration shares resources such as control logic, storage structures, and signaling mechanisms between cache control and prefetch operations, reducing overall circuit area while maintaining prefetch functionality
3Loss of time
If aggressive prefetching is performed to improve performance, then memory latency reduces, but cache eviction accuracy worsens
Solution Approach 1:
The patent implements a feedback mechanism where actual cache access outcomes are monitored and used to refine prefetch predictions. The system tracks whether prefetched blocks were actually used, and adjusts prediction behavior accordingly, improving eviction accuracy by learning from past prefetch performance while maintaining reduced memory latency
Data Source
AI summary
Disclosed techniques relate to prefetching security tag metadata. In some embodiments, metadata control circuitry stores security tag metadata for blocks of data in a memory space, wherein the metadata is stored at non-contiguous addresses relative to corresponding data blocks in the memory space and accesses and verifies the security tag metadata in conjunction with accessing a corresponding block of data. Prefetch circuitry may store, for a given access map, security tag information that indicates whether security tag metadata has been prefetched for one or more data blocks represented by the given access map. Control circuitry may, in response to determining that a set of demand requests in an access map is approaching a block boundary of a first data block whose security tag metadata has not been prefetched according to the security tag information, generate a prefetch of security tag metadata corresponding to the first data block.