GPU Cache Priority and Partitioning for Lower Access Latency
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Solution Overview
Problem
Current graphics processing units (GPUs) face challenges in optimizing cache efficiency and utilization, particularly in parallel graphics data processing, which can lead to increased access latency and reduced performance.
Innovation Solution
The proposed solution involves a system and method for improving cache efficiency by controlling first-level cache priority, partitioning shared cache usage, and implementing opt-in hardware cache coherency, specifically designed for general-purpose graphics processing units (GPGPUs).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If shared cache is used for parallel processing, then processing capacity increases, but access latency increases due to contention
Solution Approach 1:
The shared cache is segmented into multiple ways (e.g., 8-way set associative cache) where each way can be independently accessed. This segmentation allows parallel processing threads to access different cache ways simultaneously, increasing processing capacity while reducing access latency through parallel cache access paths.
Solution Approach 2:
The patent introduces a new dimension of parallelism by implementing multiple independent cache access paths (ways) within the shared cache structure. This dimensional expansion allows simultaneous access from multiple processing units without traditional contention, resolving the latency issue while maintaining high processing capacity.
2Productivity
If cache size is increased to improve utilization, then more data can be cached, but access latency increases due to larger search space
Solution Approach 1:
The large shared cache is segmented into multiple smaller ways, each capable of independent access. This segmentation allows the system to maintain a large total cache size for high utilization while providing multiple parallel access paths that reduce the effective search time, as each way can be accessed simultaneously rather than sequentially.
Solution Approach 2:
The patent implements excessive parallel access paths (more ways than strictly necessary) to ensure that even as cache size grows, access latency does not increase. By providing more access paths than the minimum required, the system maintains constant access latency while accommodating larger cache capacities.
3Reliability
If cache coherence protocols are implemented, then data consistency is improved, but processing performance deteriorates due to protocol overhead
Solution Approach 1:
Each processing unit maintains its own view of cache state and performs self-service coherence management. The independent cache ways automatically maintain consistency through their isolated access paths without requiring centralized coherence protocols, thereby maintaining data consistency while avoiding the performance overhead of traditional cache coherence mechanisms.
Data Source
AI summary
Systems and methods for improving cache efficiency and utilization are disclosed. In one embodiment, a graphics processor includes processing resources to perform graphics operations and a cache controller of a cache coupled to the processing resources. The cache controller is configured to control cache priority by determining whether default settings or an instruction will control cache operations for the cache.