GPU Write Message Cache Attributes for Low-Latency Memory Access
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Solution Overview
Problem
Current graphics processing units (GPUs) face challenges in efficiently managing cache access latency due to the virtually indexed cache, which restricts the use of page table entry-based caching control.
Innovation Solution
The implementation of instruction-based cache control for GPUs, which allows for dynamic management of cache attributes based on memory requests, enabling more efficient cache utilization and reduced latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a virtually indexed cache is used to reduce cache access latency, then cache access speed is improved, but page table entry-based caching control cannot be used
Solution Approach 1:
The patent segments the caching control mechanism into two independent parts: (1) virtual address indexing for fast cache lookup, and (2) separate write message attributes for cache control. This segmentation allows the cache to operate in two modes: fast path using virtual indexes without page table walks, and controlled path using write messages with attributes to manage cache behavior, thus resolving the contradiction between speed and adaptability
Solution Approach 2:
The patent introduces write messages as an intermediary mechanism between the GPU and cache system. These write messages carry attributes that provide caching control without requiring page table entry-based management. The write messages act as a mediator that enables flexible cache control while maintaining the performance benefits of virtual indexing
2Measurement precision
If page table entry-based caching control is used, then caching control precision is improved, but cache access latency increases
Solution Approach 1:
The patent applies preliminary action by pre-associating cache control attributes with write messages before cache operations. Instead of determining cache control during cache access (which would require page table walks), the control attributes are prepared in advance as part of the write message, enabling precise control without additional latency
Solution Approach 2:
The patent extracts the caching control functionality from the page table entry lookup process and places it into write message attributes. This separation allows cache control precision to be maintained through attribute-based management while eliminating the latency penalty of page table walks during cache access
Data Source
AI summary
Embodiments described herein provide techniques to facilitate instruction-based control of memory attributes. One embodiment provides a graphics processor comprising a processing resource, a memory device, a cache coupled with the processing resources and the memory, and circuitry to process a memory access message received from the processing resource. The memory access message enables access to data of the memory device. To process the memory access message, the circuitry is configured to determine one or more cache attributes that indicate whether the data should be read from or stored the cache. The cache attributes may be provided by the memory access message or stored in state data associated with the data to be accessed by the access message.