Pointer Load Prefetching via Dynamic Predictor Tracking

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Solution Overview

Problem

Conventional cache prefetching techniques are inefficient in identifying and prefetching data referenced by pointers, particularly in patterns like arrays of pointers, due to the random nature of memory locations and lack of discernible patterns.

Innovation Solution

A system and method that utilize a predictor to identify pointer load instructions by tracking load instructions and their data access patterns, allowing for the prefetching of both pointer and data references, thereby reducing latency in data access.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional prefetching techniques are used, then simple sequential access patterns are handled well, but pointer-referenced data with random memory locations cannot be effectively prefetched

Engineering Contradiction:

Improveprefetching accuracyVSAvoidability to handle pointer-referenced data

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The system dynamically adapts its prefetching behavior based on the type of memory access detected. When pointer load instructions are identified, the system switches to a specialized prefetching mode that tracks pointer targets and prefetches both the pointer and the referenced data, whereas sequential accesses continue to use traditional stride-based prefetching.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the prefetching parameters based on the access pattern detected. For pointer-referenced data, it modifies the prefetching strategy to include dual prefetching (pointer and data), adjusts confidence level thresholds, and changes how memory addresses are tracked and compared, thereby adapting to the specific characteristics of pointer-based access patterns.

Inventive Principle:

Principle #35Parameter changes

2Loss of time

If dual prefetching is implemented for pointer and data, then latency is reduced, but system complexity increases

Engineering Contradiction:

Improvedata access latencyVSAvoidprefetcher complexity

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The prefetching system serves itself by using the pointer load instruction information to automatically generate the second prefetch request for the referenced data. The system tracks the relationship between pointer loads and data loads, and autonomously issues prefetch requests without requiring external control, thereby reducing the complexity overhead.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The system performs preliminary prefetching of both the pointer and the referenced data before they are actually needed by the execution unit. By anticipating the need for pointer-referenced data and fetching it in advance, the system reduces latency while the modular architecture keeps complexity manageable.

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If pointer load instructions are tracked and identified, then prefetching accuracy improves, but detection and measurement difficulty increases

Engineering Contradiction:

Improvepointer identification accuracyVSAvoidpointer load instruction detection

Core Design Contradiction:

Measurement precisionVSDifficulty of detecting and measuring

Solution Approach 1:

The system uses feedback from matched memory addresses to identify pointer load instructions. When a data load instruction accesses a memory location that matches a previously fetched pointer value, the system reinforces the identification of the original load as a pointer load instruction, improving detection accuracy through iterative feedback.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system replaces complex pattern recognition and analysis mechanisms with a simpler address-matching mechanism. Instead of analyzing pointer patterns or making complex predictions about random access sequences, the system simply compares memory addresses against previously fetched pointer values, significantly reducing detection difficulty.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS12216581B2System, method, and apparatus for enhanced pointer identification and prefetching

Publication Date: 2025.02.04 INTEL CORP

AI summary

System and method for prefetching pointer-referenced data. A method embodiment includes: tracking a plurality of load instructions which includes a first load instruction to access a first data that identifies a first memory location; detecting a second load instruction which accesses a second memory location for a second data, the second memory location matching the first memory location identified by the first data; responsive to the detecting, updating a list of pointer load instructions to include information identifying the first load instruction as a pointer load instruction; prefetching a third data for a third load instruction prior to executing the third load instruction; identifying the third load instruction as a pointer load instruction based on information from the list of pointer load instructions and responsively prefetching a fourth data from a fourth memory location, wherein the fourth memory location is identified by the third data.