Shared Buffer Free List Logic for GPU Memory Bandwidth Reduction
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Solution Overview
Problem
Modern GPU pipelines face challenges in efficiently implementing data storage buffers, leading to performance deficiencies and increased hardware expenses due to their complex nature.
Innovation Solution
A system utilizing a shared buffer with free list logic, FIFO logic, pipeline logic, and pointer logic to manage attribute values and pointers, allowing for efficient data processing and memory management by discarding rejected primitive data and maintaining availability of memory in the common buffer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple FIFO buffers are used in GPU pipeline stages, then data processing capability is improved, but hardware cost and device complexity increase
Solution Approach 1:
The patent merges multiple separate FIFO buffers into a single shared buffer that is commonly accessed by multiple pipeline stages. Instead of having dedicated FIFOs at each stage (vertex shader, geometry shader, rasterizer, etc.), a single shared buffer is implemented with multiple pointers that can simultaneously access different portions of the buffer, thereby reducing hardware complexity while maintaining processing capability
Solution Approach 2:
The shared buffer serves multiple functions and multiple pipeline stages simultaneously. A single buffer structure is designed to support vertex attribute storage, primitive assembly, rasterization data, and fragment processing across different pipeline stages, making the buffer universal and eliminating the need for stage-specific buffers
2Productivity
If multiple FIFO buffers are used in GPU pipeline stages, then data processing capability is improved, but memory bandwidth usage increases
Solution Approach 1:
By combining multiple FIFO buffers into one shared buffer, the system eliminates redundant memory allocations and reduces the total volume of data that needs to be transferred across memory boundaries. Multiple pipeline stages can access the same physical memory location without requiring duplicate data copies, thereby reducing overall memory bandwidth consumption
Solution Approach 2:
Instead of physically copying data between multiple FIFO buffers at different pipeline stages, the system uses pointer copying and indirect access. Each pipeline stage maintains a pointer to the shared buffer and accesses data through these pointers, eliminating the need for actual data copying and reducing memory bandwidth usage
3Device complexity
If a shared buffer is used instead of multiple FIFO buffers, then hardware complexity is reduced, but data processing efficiency may worsen
Solution Approach 1:
The shared buffer is logically segmented into multiple regions or slots that can be independently accessed by different pipeline stages. Each pipeline stage is assigned specific buffer regions or time slots, allowing parallel access without conflict. This segmentation maintains processing efficiency while using a single physical buffer structure
Solution Approach 2:
The system implements dynamic pointer management where buffer pointers are adjusted in real-time based on data production and consumption rates at different pipeline stages. This dynamic allocation and pointer advancement allows flexible data flow management, preventing bottlenecks and maintaining high processing efficiency despite using a shared buffer
4Quantity of substance
If rejected primitive data is retained in the buffer, then memory availability is reduced, but data processing completeness is improved
Solution Approach 1:
The system implements a mechanism to identify and discard rejected primitive data from the shared buffer. When primitives are determined to be outside the view frustum or otherwise invalid, their corresponding buffer entries are marked for discarding and eventually removed, freeing up memory space for new data while ensuring that only valid primitives are processed further
Solution Approach 2:
The system uses feedback from later pipeline stages (such as rasterization rejection or fragment processing results) to inform earlier stages about which data should be discarded. This feedback loop allows the buffer management system to identify and remove rejected primitive data, optimizing memory availability while maintaining processing completeness for valid data
Data Source
AI summary
Provided are methods and systems for reducing memory bandwidth usage in a common buffer, multiple FIFO computing environment. The multiple FIFO's are arranged in coordination with serial processing units, such as in a pipeline processing environment. The multiple FIFO's contain pointers to entry addresses in a common buffer. Each subsequent FIFO receives only pointers that correspond to data that has not been rejected by the corresponding processing unit. Rejected pointers are moved to a free list for reallocation to later data.