Graphics Processor Color-State Mapping for Efficient Fragment Caching
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Solution Overview
Problem
Graphics processors face inefficiencies in cache usage due to redundant storage of pixel data, particularly in multi-sample anti-aliasing, leading to performance degradation and increased power consumption.
Innovation Solution
Implementing a two-level metadata structure that maps samples in a region of pixels to colors using color state metadata and region slab state metadata, allowing efficient cache access by storing shared color data in a single element and mapping different regions to subsets of color state metadata.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple samples of a pixel are stored with their respective color data, then each sample can be processed independently for anti-aliasing, but redundant color data is stored when multiple samples have the same color, leading to inefficient cache usage
Solution Approach 1:
The patent merges color data storage by creating a shared color buffer that stores color values once and uses indexing to reference them from multiple sample locations. Instead of storing identical color data in each sample's storage location, the system combines redundant color representations into a single shared storage structure with reference pointers, directly reducing cache memory usage while preserving anti-aliasing processing capability
Solution Approach 2:
The shared color buffer serves multiple functions: it stores color data for multiple samples, provides a compression mechanism for redundant colors, and maintains random access capability through indexing. This universal storage structure replaces multiple dedicated color buffers, improving cache efficiency without sacrificing the ability to process individual samples independently for anti-aliasing
2Ease of operation
If color data is stored redundantly for each sample, then cache access is straightforward, but power consumption increases due to unnecessary data storage and transfer
Solution Approach 1:
The patent extracts the redundant color data from individual sample storage locations and places it in a shared color buffer. By separating the unique color information from the sample-specific data, the system eliminates unnecessary data duplication while maintaining straightforward access through indexing mechanisms, thereby reducing the amount of data that needs to be stored and transferred, which directly lowers power consumption
3Speed
If redundant color data is stored in cache, then all sample color information is immediately available, but cache thrashing occurs reducing processing performance
Solution Approach 1:
By merging redundant color data into a shared buffer with centralized storage, the system reduces the total volume of data in the cache. This consolidation eliminates cache thrashing caused by redundant data occupying cache lines, while the indexing mechanism ensures that color data access speed is maintained through direct pointer-based retrieval from the shared structure
4Adaptability or versatility
If each sample stores its own color data, then sample independence is maintained, but memory bandwidth is consumed by redundant data transfers
Solution Approach 1:
The shared color buffer provides a universal storage location that serves all samples while maintaining sample processing independence through indexing. Each sample can still be processed independently by referencing its corresponding color index in the shared buffer, eliminating the need for redundant data transfers between memory and cache, thereby reducing memory bandwidth consumption without sacrificing processing flexibility
Data Source
AI summary
Techniques are disclosed relating to storage techniques for fragment data. In some embodiments, one or more storage circuits are configured to store sample color data for processing by shader processors including a data structure that includes first and second elements configured to store color data for first and second colors, respectively. In some embodiments, control circuitry is configured to generate color state metadata to map samples in a region of pixels to colors in elements of the data structure, including to map multiple samples to the first element of the data structure. In some embodiments, control circuitry is configured to access the color state metadata to determine a mapped element of the data structure for a given sample and read the color data from the mapped element of the data structure. Disclosed techniques may improve, reduce or avoid duplication and thereby improve cache efficiency for accesses to color data.