Cache Line Bank Segmentation for Atomic Write Conflicts
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Solution Overview
Problem
High-level shader languages lack a mechanism to write scattered bytes or words to a buffer, leading to performance reductions due to same-address atomic conflicts and dependency chains in the load/store/cache architecture of graphics processors.
Innovation Solution
Implementing multi-render partitioning techniques that allow logical or physical partitioning of a graphics processor, enabling separate render command streams and resource allocation to render partitions, which helps in efficient processing of graphics and compute operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If byte/word writes are emulated via double word atomic operation with byte-mask, then write capability is provided, but same-address atomic conflict occurs reducing performance
Solution Approach 1:
The cache line is segmented into multiple banks (e.g., 4 banks of 64 bytes each). Atomic operations are routed to specific banks based on the address, allowing parallel processing of operations that would otherwise conflict on the same address. This segmentation eliminates same-address atomic conflicts by distributing operations across different banks.
Solution Approach 2:
The patent introduces a new dimension of parallelism by organizing cache memory into multiple banks that can operate independently. Instead of sequential atomic operations on a single cache line, the system uses bank indexing to create parallel execution paths, transforming a one-dimensional sequential operation into a multi-dimensional parallel structure.
2Ease of operation
If multiple partial atomic writes are performed to the same cache line, then fine-grained control is achieved, but dependency chain is created reducing cache access performance
Solution Approach 1:
The cache line is divided into multiple independent banks, each capable of handling atomic operations independently. Partial writes are routed to specific banks based on their address ranges, allowing concurrent execution of operations that would otherwise create dependency chains. This segmentation breaks the dependency chain by enabling parallel access to different bank portions.
Solution Approach 2:
The patent introduces bank indexing as an intermediary layer between the atomic operation request and the actual cache memory. This intermediary routes operations to appropriate banks, preventing direct conflicts and dependency chains while maintaining fine-grained control. The bank index acts as a mediator that enables parallel execution without compromising operational precision.
Data Source
AI summary
Embodiments described herein provide a technique to merge partial cache line writes to a cache memory. One embodiment provides a graphics processor comprising a graphics core, a cache coupled with the graphics core, and memory access circuitry to process memory access messages received from the graphics core. The memory access circuitry includes partial cache line write merge circuitry configured to merge a first partial write to a cache line of the cache with a second partial write to the cache line of the cache.