Prefetch Apparatus Region Tracking Memory Latency
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Solution Overview
Problem
Existing prefetching technologies face challenges in identifying complex access patterns and reducing latency due to out-of-order issues and compiler optimizations, which complicate the prediction of memory access requests.
Innovation Solution
The proposed solution involves a prefetch apparatus that categorizes memory space into regions, uses request tracking storage to update access information, and initiates a region prefetching process when a sufficient number of access requests are detected in an adjacent region, allowing for 'page mode' prefetching even with complex patterns, thereby reducing latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If traditional prefetching circuitry monitors load requests to identify access patterns, then data items can be retrieved from memory before requests are received, but the complexity of identifying complex access patterns increases due to out-of-order issues and compiler optimizations
Solution Approach 1:
The patent segments the complex memory address space into multiple regions, with each region tracked by a dedicated region entry in the request tracking storage. This segmentation allows the prefetching circuitry to independently monitor and identify access patterns within each region, simplifying the overall pattern recognition task by breaking it down into smaller, more manageable regional analyses rather than attempting to analyze the entire memory space as a single complex system.
2Loss of time
If prefetching circuitry generates prefetch requests based on identified patterns, then data retrieval latency is reduced, but the accuracy of pattern prediction decreases when faced with out-of-order issues and compiler optimizations
Solution Approach 1:
The patent applies local quality by maintaining different types of information in each region entry tailored to the specific access patterns of that region. Each region entry stores access counts and region identifiers specific to its local memory region, allowing the prefetching circuitry to make locally optimized predictions for each region rather than applying a single global prediction rule. This local customization improves prediction accuracy for diverse access patterns while still reducing latency through prefetching.
3Productivity
If region-based prefetching is implemented to simplify pattern identification, then prefetching efficiency improves, but the ability to handle fine-grained access requests within regions may be reduced
Solution Approach 1:
The patent adds a regional dimension to the prefetching architecture by introducing region identifiers and region entries as an intermediate layer between the fine-grained access requests and the prefetching logic. This dimensional transformation allows the system to aggregate access patterns at the region level for efficient pattern identification while still maintaining the ability to generate precise prefetch requests for individual addresses within regions, effectively resolving the contradiction between efficiency and precision through hierarchical organization.
Data Source
AI summary
Prefetch apparatus and a method of prefetching are presented. The prefetch apparatus monitors access requests, each having an access request address, and has request tracking storage to store region entries for regions of memory space which each span multiple access request addresses. The request tracking storage keeps access information for access requests received in their corresponding region entries. When a new region access request is received, which belongs to a new region for which there is no region entry, and when the request tracking storage has an adjacent region entry for which the access information shows that at least a predetermined number of the access request addresses have been accessed, a page mode region prefetching process is initiated for all access request addresses in the new region.