Strided Block Transfer Instruction for Cache Memory
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Solution Overview
Problem
Conventional graphics processing systems burden the central processing unit (CPU) with software loops for block transfers between memory, and misalignment issues arise due to differing memory pitches, necessitating an improved technique for efficient block data transfer.
Innovation Solution
The implementation of a strided block transfer instruction that allows for the transfer of data blocks between memory and cache or video memory using a single CPU execution, utilizing registers to manage source and destination pitches and line numbers, thereby optimizing CPU efficiency and handling misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the CPU uses a software loop to transfer data line by line from source memory to destination memory, then the block transfer can be completed, but the CPU workload becomes significant and processing efficiency decreases
Solution Approach 1:
The block transfer operation is segmented into multiple cache lines, where each cache line can be transferred independently. The system divides the source block into multiple cache lines and transfers them to corresponding destination cache lines, allowing parallel processing and reducing the CPU's sequential processing burden.
Solution Approach 2:
The system performs preliminary actions by pre-fetching cache lines from source memory into the cache before the actual block transfer is needed. This allows the cache to be pre-populated with data that will be transferred to video memory, reducing the CPU's real-time processing workload during the critical transfer path.
2Adaptability or versatility
If the source memory and destination memory have different pitches, then the block transfer can accommodate misalignment, but additional complexity is required to handle the misalignment
Solution Approach 1:
The system applies different handling strategies to different parts of the block transfer based on local pitch requirements. Each cache line transfer can have its own source and destination pitch values, allowing the system to handle misalignment locally at each cache line boundary rather than requiring complex global alignment calculations for the entire block.
Solution Approach 2:
The pitch values for source and destination cache lines are made dynamic rather than fixed. The system can adjust the pitch values on a per-cache-line basis to accommodate varying misalignment conditions, allowing flexible adaptation to different memory configurations without requiring a single complex alignment solution for the entire block.
3Reliability
If the CPU has access to TLBs and page tables for virtual address translation, then address translation can be performed, but the graphics hardware cannot access these resources directly
Solution Approach 1:
The CPU acts as an intermediary between the graphics hardware and the TLBs/page tables. The CPU executes the block transfer instruction that performs virtual address translation using its access to TLBs and page tables, then transfers the translated data through the cache to video memory. This mediator approach allows graphics operations to benefit from address translation without requiring direct hardware access to translation resources.
Solution Approach 2:
The CPU serves itself by executing the block transfer instruction that handles both the address translation and the data transfer in one operation. Rather than requiring separate graphics hardware to access TLBs/page tables, the CPU performs the translation and transfer as a self-contained operation, eliminating the need for graphics hardware to directly access translation resources.
Data Source
AI summary
A method includes determining a cache width of a cache of a processing device and determining a block size of image data processed by the processing device. The method further includes prefetching a data block of image data from a memory component to a plurality of cache lines of the cache based on the cache width and the block size. A processing system includes a memory component, a cache and an execution pipeline coupled to the memory component and the cache. The execution pipeline is to determine a cache width of the cache, determine a block size of image data stored at the memory component, and prefetch a data block of image data from a memory component to a plurality of cache lines of the cache based on the cache width and the block size.