Asynchronous Input Dependency Resolution for GPU Workloads
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Solution Overview
Problem
Modern Deep Neural Network training workloads face challenges in efficiently managing dependencies due to the limitations of hardware synchronization instructions, which can stall forward progress on GPUs and lead to inefficiencies in command buffer execution.
Innovation Solution
An asynchronous input dependency resolution mechanism is introduced, which augments thread dispatch hardware with additional dependency resolution capabilities. This mechanism allows for concurrent workload scheduling by providing a list of dependencies to be managed during thread dispatch, using flag or indicator bits to indicate dependencies that need resolution, and employing deferred or immediate submission modes for intelligent handling of data dependencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hardware synchronization instruction is used to manage dependencies, then dependency management is achieved, but forward progress on GPU is stalled
Solution Approach 1:
The patent introduces a software-based dependency management system that acts as an intermediary between the GPU execution engine and the dependency resolution logic. This intermediary layer processes dependency graphs and schedules commands asynchronously, allowing the GPU to continue executing independent operations while dependencies are resolved in the background, thus eliminating stalls while maintaining reliable dependency management
Solution Approach 2:
The system performs preliminary action by pre-processing dependency graphs and preparing command buffers before actual GPU execution. Dependencies are resolved and command buffers are prepared in advance, allowing the GPU to receive ready-to-execute commands without waiting for dependency resolution during execution, thereby maintaining forward progress while ensuring dependency correctness
2Reliability
If hardware synchronization instruction is used, then dependency management is achieved, but unrelated commands are stalled
Solution Approach 1:
The patent segments the dependency management function from the command execution function. Instead of using a single hardware synchronization instruction that affects all commands, the system divides dependency resolution into separate software-managed units. Each command buffer can be independently tracked and executed, allowing unrelated commands to proceed in parallel while maintaining reliable dependency management through the segmented dependency graph structure
Solution Approach 2:
The system implements dynamic dependency resolution where the execution schedule is adjusted in real-time based on actual dependency status. Unrelated commands are not stalled but rather dynamically scheduled to execute as soon as their dependencies are resolved, improving command execution efficiency while maintaining reliable dependency management through flexible scheduling
3Device complexity
If single stalling semaphore is used per command buffer, then hardware simplicity is maintained, but multiple levels of parallelism are limited
Solution Approach 1:
The patent changes the fundamental parameter of dependency management from hardware-based fixed semaphores to software-based flexible dependency graphs. This parameter change allows the system to support multiple levels of parallelism by representing dependencies as directed acyclic graphs rather than linear semaphore waits, enabling complex parallel workloads while maintaining manageable system complexity through software abstraction
Solution Approach 2:
The software-based dependency management system provides universal functionality that can handle various parallelism scenarios (single-level, multi-level, fine-grained, coarse-grained) through a single unified approach. The same dependency graph mechanism works for all types of parallel workloads, making the system highly adaptable while avoiding the need for multiple specialized hardware mechanisms
Data Source
AI summary
Described herein is a graphics processor configured to perform asynchronous input dependency resolution among a group of interdependent workloads. The graphics processor can dynamically resolve input dependencies among the workloads according to a dependency relationship defined for the workloads. Dependency resolution be performed via a deferred submission mode which resolves input dependencies prior to thread dispatch to the processing resources or via immediate submission mode which resolves input dependencies at the processing resources.