Address Translation Cache Arbitration for GPU Performance
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Solution Overview
Problem
Current address translation techniques in graphics processing units (GPUs) face performance bottlenecks due to head-of-line blocking, limited scheduling flexibility, and increased latency for latency-sensitive requests, particularly in scenarios with cache misses and hazards, leading to reduced bandwidth and system-level performance drops.
Innovation Solution
The implementation of independent arbitration techniques in address translation circuitry allows requests to the same cache block to proceed independently, reducing head-of-line blocking and prioritizing latency-sensitive requests by using a miss identifier and hazard content addressable memory (CAM) to manage dependencies and reordering of memory accesses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional address translation arbitration is used, then cache block access is controlled sequentially, but head-of-line blocking occurs and scheduling flexibility is limited
Solution Approach 1:
The patent segments the arbitration process by introducing separate arbitration queues for different request types (e.g., TLB miss requests vs. other requests). This allows independent arbitration of different request streams, eliminating head-of-line blocking while maintaining manageable control complexity through structured queue management.
Solution Approach 2:
The patent implements dynamic scheduling by allowing the arbitration logic to adaptively select between different request types based on current system state. The hazard detection mechanism dynamically adjusts arbitration decisions to prevent hazards while maximizing throughput, creating a flexible and responsive arbitration system.
2Reliability
If sequential arbitration of cache block requests is used, then access order is maintained, but latency-sensitive requests experience increased latency
Solution Approach 1:
The patent segments the request processing paths by creating separate queues for TLB miss requests and other requests. This segmentation allows TLB miss requests to be processed independently without being blocked by other request types, reducing latency while maintaining data consistency through hazard detection.
Solution Approach 2:
The patent employs hazard detection as a feedback mechanism that monitors request dependencies and adjusts arbitration decisions accordingly. When hazards are detected, the system feedbacks by reordering or blocking specific requests to maintain data consistency, while allowing latency-sensitive requests to proceed when safe, thus reducing overall latency.
3Productivity
If independent arbitration is implemented, then head-of-line blocking is reduced, but arbitration control logic becomes more complex
Solution Approach 1:
The patent manages complexity by segmenting the arbitration control logic into distinct modules: separate queues for different request types, dedicated hazard detection logic, and structured arbitration decision-making. This modular segmentation makes the complex independent arbitration system more manageable and maintainable while achieving improved throughput.
4Reliability
If strict request ordering is enforced, then data consistency is maintained, but system performance and bandwidth are reduced
Solution Approach 1:
The patent uses hazard detection as a feedback mechanism that continuously monitors request dependencies. When hazards are detected, the system responds by selectively blocking or reordering requests to maintain data consistency. This feedback approach allows the system to maintain consistency only when necessary, permitting parallel processing and higher bandwidth when no hazards are present.
Solution Approach 2:
The patent implements dynamic ordering where the request processing order adapts based on hazard conditions. The system transitions between strict ordering (when hazards are detected) and relaxed ordering (when requests are independent), optimizing both data consistency and system bandwidth by applying ordering constraints only when necessary.
Data Source
AI summary
Techniques are disclosed relating to caching for address translation. In some embodiments, address translation circuitry is configured to process requests to translate addresses in a first address space to addresses in a second address space. The translation circuitry may include cache circuitry configured to store translation information, arbitration circuitry configured to arbitrate among ready requests for access to entries of the cache, and hazard circuitry. The hazard circuitry may assign a first request to an ready status the arbitration circuitry based on detection of an absence of hazards for a first address of the first request and add a second request to a queue of requests for the arbitration circuitry based on detection of a hazard for a second address of the second request. Independent arbitration for requests without hazards may improve performance in various aspects, relative to traditional techniques.