Indirect Cache Prefetching via Address Hint Association
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Solution Overview
Problem
Existing cache prefetching technologies struggle to accurately predict future memory access requests in certain access patterns, leading to reduced performance improvements.
Innovation Solution
An apparatus and method that associate an indirect prefetch condition with a first memory access request, using hint information to anticipate that the data accessed will be address indicating data for a subsequent memory access request, and generate a second address for prefetching based on available address indicating data in the cache.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional prefetching is used to predict future memory access requests, then cache hit rate is improved, but prediction accuracy deteriorates in certain access patterns
Solution Approach 1:
The patent applies preliminary action by issuing prefetch requests before the actual memory access requests are made. The system predicts future memory access addresses and pre-loads the data into the cache, so that when the actual access occurs, the data is already available in the cache, improving cache hit rate and reducing memory access latency.
Solution Approach 2:
The patent introduces an intermediary mechanism - a buffer - that stores predicted memory access addresses. This buffer acts as a mediator between the prefetching logic and the cache, allowing the system to manage and track predicted addresses separately, improving the overall prediction accuracy by maintaining a record of anticipated memory access patterns.
2Speed
If prefetching is implemented to reduce cache misses, then memory access speed is improved, but system complexity increases
Solution Approach 1:
The patent segments the memory access system into distinct components: the prefetching unit that generates predicted addresses, the buffer that stores these predictions, and the cache that holds the actual data. This segmentation allows each component to be optimized independently and simplifies the overall system architecture by clearly defining the responsibility of each part.
Solution Approach 2:
The system performs preliminary actions by predicting and preparing memory access addresses before they are actually needed. This allows the cache to be pre-filled with data, reducing the latency of actual memory accesses and improving overall system speed without requiring fundamental changes to the memory hierarchy.
3Reliability
If prefetch requests are issued to predict arbitrary memory addresses, then cache utilization is improved, but prediction difficulty increases
Solution Approach 1:
The buffer serves as an intermediary that simplifies the prediction process for arbitrary memory addresses. Instead of directly predicting complex arbitrary addresses, the system uses the buffer to store and manage intermediate prediction results, making it easier to track and refine predictions for irregular access patterns.
Solution Approach 2:
The system performs preliminary prediction actions for arbitrary memory addresses by analyzing access patterns and generating predicted addresses in advance. This preliminary action allows the cache to be proactively filled with data that would otherwise be difficult to predict, improving cache utilization for irregular access patterns.
Data Source
AI summary
An apparatus comprises associating circuitry to associate an indirect prefetch condition with a memory access request when hint information indicates that the data to be accessed in response to the memory access request is address indicating data which is to be used to generate a second address for a subsequent memory access request. A second address can be generated using the address indicating data, and a prefetch memory access request can be issued to seek to make data at the second address available in the associated cache.