Hardware-Guided Software Prefetch Insertion Without Warm-Up
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Solution Overview
Problem
Hardware prefetchers struggle with irregular memory accesses, requiring a warm-up period to identify patterns, while software prefetching lacks precision in timing, making it challenging to optimize memory access efficiently.
Innovation Solution
A system that identifies target code locations for software prefetching based on hardware prefetcher events, using ablation studies to determine prefetch-friendly and unfriendly functions, enabling software prefetchers to insert instructions without a warm-up period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If hardware prefetchers are used to identify memory access patterns, then prefetching accuracy is improved, but a warm-up period is required which delays pattern identification
Solution Approach 1:
The system performs preliminary analysis during compilation to identify potential prefetch opportunities in advance, rather than relying on runtime pattern detection. The compiler analyzes control flow graphs and data dependency information to determine which memory accesses should be prefetched, eliminating the need for a warm-up period while maintaining accurate prefetching decisions
Solution Approach 2:
The invention introduces an intermediary component (prefetch insertion component) that bridges the gap between hardware prefetcher capabilities and software implementation. This component uses hardware prefetcher performance data and ablation study results to guide software prefetch instruction insertion, combining the accuracy of hardware analysis with the immediacy of software execution
2Adaptability or versatility
If software prefetching is used for irregular memory accesses, then adaptability is improved, but precision in timing prefetch instructions deteriorates
Solution Approach 1:
The system implements feedback mechanisms where hardware prefetcher performance metrics and cache event data are collected and analyzed to refine software prefetch insertion decisions. Ablation studies compare system performance with and without hardware prefetchers to identify code locations that would benefit from software prefetching, creating a feedback loop that improves timing precision for software prefetch instructions
3Measurement precision
If hardware prefetchers are active, then memory access patterns are identified accurately, but system complexity increases
Solution Approach 1:
The invention extracts the essential pattern identification functionality from complex hardware prefetchers and translates it into software-based solutions. By analyzing hardware prefetcher behavior and extracting key patterns, the system generates software prefetch instructions that replicate the benefits of hardware prefetching without requiring the full hardware infrastructure, thereby reducing system complexity
Data Source
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AI summary
Generally disclosed herein is an approach for identifying target code locations for software prefetching instructions based on hardware prefetching information. The target code locations can be identified based on the locations where the hardware prefetchers were designed to prefetch loads. Hardware cache events related to processor events for different caches can be monitored for cache misses in a system running when hardware prefetchers are active and inactive. Code locations that may benefit from the use of the hardware prefetchers may be determined based on an ablation study. The identified code locations may be treated as recognized memory access patterns. Software prefetchers can be configured to use these memory access patterns for prefetching data while avoiding an extended time required to identify memory access patterns (i.e. a warm-up period) and fetching in locations where hardware prefetching is beneficial.