GPU Texture Sampler Queues for Out-of-Order Cache Processing
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Solution Overview
Problem
Existing GPU texture sampler operations are limited by latency sensitivity due to the variability in operation length, leading to inefficiencies in cache storage and thread management, which previous solutions have not effectively addressed.
Innovation Solution
Implementing an out-of-order execution mechanism for GPU texture sampler operations using virtual channels (VC) that arbitrate transactions once data is present in the L1 cache, with a latency queue and multiple VC queues to facilitate out-of-order processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an in-order pipeline is used for texture sampler operations, then the implementation is simpler, but the performance is significantly impacted by latency increases
Solution Approach 1:
The patent implements a hybrid approach where the texture sampler unit can dynamically switch between in-order and out-of-order execution modes. The pipeline maintains in-order execution for simplicity but introduces out-of-order transaction processing specifically for cache miss scenarios, allowing the system to adapt its execution strategy based on operational needs and latency conditions
Solution Approach 2:
The patent segments the texture sampler pipeline into distinct functional components: an in-order issue stage for simplicity, and a separate out-of-order transaction processing stage using virtual channels. This segmentation allows the simple in-order frontend to coexist with the performance-optimized out-of-order backend, resolving the contradiction between implementation simplicity and performance
2Reliability
If cache hierarchy misses occur, then memory operation latency increases, but the in-order pipeline cannot handle this latency effectively
Solution Approach 1:
The patent introduces virtual channels as an intermediary mechanism between the texture sampler unit and the cache hierarchy. These virtual channels buffer and manage memory transactions, allowing the system to decouple the texture sampling operations from cache miss latency. When cache misses occur, the virtual channels handle the delayed transactions without stalling the entire pipeline, thus mitigating the time loss while maintaining cache reliability
3Productivity
If the 3D pipeline size and complexity increase, then processing capability improves, but memory operation latency increases
Solution Approach 1:
The patent adds a new dimension to the traditional 3D pipeline by introducing out-of-order execution capabilities specifically for texture sampler operations. This dimensional addition allows the pipeline to process memory transactions in a different temporal order than they were issued, enabling complex 3D graphics processing to proceed without being bottlenecked by sequential memory latency
Data Source
AI summary
Embodiments described herein are generally directed facilitating out-of-order execution of GPU texture sampler operations. An embodiment of a method includes a texture sampler of a GPU maintaining (i) a latency queue operable to store information regarding a set of transactions associated with each of multiple texture sampler operations and (ii) multiple virtual channel (VC) queues each operable to store information regarding transactions for a respective single texture sampler operation at a time. Out-of-order processing of the texture sampler operations is facilitated by making use of the latency queue and the VC queues. For example, during a transaction processing interval, the availability of data in a cache for the transactions associated with each of the VC queues may be determined. A VC queue may be selected based on the determined availability of data. A transaction associated with a head of the selected VC queue may then be processed.