Graphics Pipeline Prefetching for Cache Miss Reduction
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Solution Overview
Problem
3D graphics pipelines experience increased latency and stalling due to cache memory misses when rendering scenes, particularly when spans in triangles change, leading to performance degradation.
Innovation Solution
Prefetching data for the next span into the cache memory while processing the current span, using a rasterizer and processor to calculate coordinates and addresses based on fragment information, and an address generator to determine optimal cache access states for prefetching from external memory devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cache memory is used to store data addresses and data in advance, then the likelihood of stall is decreased, but cache memory miss probability ratio increases with span change
Solution Approach 1:
The patent implements preliminary action by prefetching data for the next span into the cache memory while the current span is being processed. The address generator calculates the address of the first data of the next span in advance, and the controller transmits this address to the cache memory to prefetch data from external memory devices before it is actually needed, thereby reducing cache misses when span changes occur
Solution Approach 2:
The patent applies dynamics by making the prefetching mechanism adaptive to changing spans. The address generator dynamically calculates addresses based on fragment information and span changes, while the controller adaptively manages cache memory operations according to the operational state. This dynamic approach allows the system to respond to varying rendering conditions and maintain optimal cache performance
2Loss of information
If data is read from external memory device in advance, then data availability is improved, but latency increases when span changes
Solution Approach 1:
The system performs preliminary data loading by calculating the address of the first data of the next span in advance and prefetching it into the cache memory while the current span is being processed. This ensures data is available when needed without waiting for sequential access, thereby reducing latency during span transitions
Solution Approach 2:
The patent introduces an intermediary mechanism through the cache memory itself, which acts as a buffer between external memory devices and the graphics pipeline. The controller manages this intermediary to coordinate prefetching operations, ensuring that data is loaded from external memory into the cache at optimal times without creating unnecessary latency
3Productivity
If prefetching is implemented, then cache miss occurrences are reduced, but device complexity increases
Solution Approach 1:
The patent merges the prefetching functionality into the existing graphics processing architecture by integrating the address generator and controller with the rasterizer and cache memory. Rather than adding a completely separate system, the prefetching mechanism is combined with span processing operations, where the address generator works alongside the rasterizer and the controller coordinates with the cache memory, thereby reducing overall system complexity
Solution Approach 2:
The address generator serves multiple functions: it generates addresses for the current span processing and simultaneously calculates addresses for the next span prefetching. The controller also performs multiple tasks including managing cache operations, coordinating prefetching, and monitoring operational states. This multi-functionality reduces the need for separate dedicated components, thereby reducing device complexity
Data Source
AI summary
An apparatus according to an example embodiment of the present invention, may process data of a present span. During processing, data corresponding to an address of the start data of the next span may be prefetched from the external memory device based on information related to the presently processed data. The prefetched data may store in the cache memory.