Hardware Tracking Table for Shared Memory Hazard Detection

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Solution Overview

Problem

Traditional race detection schemes in multi-threaded environments are inadequate for handling thousands of concurrent threads, leading to high false positives and inability to accurately detect data access hazards due to reliance on static analysis and simulation, which do not reflect actual hardware execution.

Innovation Solution

A computer-implemented method and system that uses a tracking table with initialization and state tracking bits to identify and report race conditions by mapping shared memory locations to hardware units, allowing for online detection and filtering of hazards, reducing false positives and enabling detection in optimized applications without source code availability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If static analysis or simulation based approaches are used for race detection, then detection completeness may be improved, but the system becomes unsuitable for handling thousands of concurrent threads and does not reflect actual hardware execution

Engineering Contradiction:

Improverace condition detection accuracyVSAvoidability to handle concurrent threads

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent replaces software-based static analysis and simulation systems with a hardware-based detection system. The tracking table and hazard detection logic are implemented in hardware (e.g., in the GPU or accompanying processing system), allowing real-time detection of race conditions during actual execution. This hardware implementation can efficiently handle thousands of concurrent threads while providing accurate detection that reflects actual hardware behavior, resolving the contradiction between detection accuracy and scalability to massive thread counts.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If comprehensive hazard reporting is implemented, then detection coverage is improved, but the rate of false positives increases significantly

Engineering Contradiction:

Improvehazard detection coverageVSAvoidfalse positive rate

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent performs preliminary actions by initializing the tracking table before execution and systematically tracking each shared memory access as it occurs. The initialization bit and access type bits are pre-configured and updated in real-time, allowing the system to distinguish between legitimate hazards and false positives. This preliminary tracking and systematic approach enables comprehensive hazard detection while filtering out false positives through actual execution observation rather than theoretical analysis.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements feedback mechanisms where the tracking table continuously monitors shared memory accesses and provides real-time information about access patterns. The hazard detection logic uses this feedback to dynamically identify actual race conditions versus false positives. The system learns from actual execution behavior, adjusting its detection based on observed access patterns, which reduces false positives while maintaining comprehensive coverage.

Inventive Principle:

Principle #23Feedback

3Speed

If tracking data is stored on the device during execution, then real-time detection capability is improved, but device memory usage and complexity increase

Engineering Contradiction:

Improvedetection response timeVSAvoidtracking infrastructure requirements

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The patent segments the tracking infrastructure by creating a tracking table with specific entries for each shared memory location. Each entry is independently managed with specific bits for initialization status and access type tracking. This segmentation allows the system to track only the necessary information for each memory location without requiring comprehensive monitoring of all system state, reducing overall complexity while enabling real-time detection through localized tracking.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS9038080B2Method and system for heterogeneous filtering framework for shared memory data access hazard reports

Publication Date: 2015.05.19 NVIDIA CORP

AI summary

A system and method for detecting, filtering, prioritizing and reporting shared memory hazards are disclosed. The method includes, for a unit of hardware operating on a block of threads, mapping a plurality of shared memory locations assigned to the unit to a tracking table. The tracking table comprises initialization information for each shared memory location. The method also includes, for an instruction of a program within a barrier region, identifying a potential conflict by identifying a second access to a location in shared memory within a block of threads executed by the hardware unit. First information associated with a first access and second information associated with the second access to the location is determined. Filter criteria is applied to the first and second information to determine whether the instruction causes a reportable hazard. The instruction is reported when it causes the reportable hazard.