Prefetch Instruction Ignoring Cache Hits for Image Processing
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Solution Overview
Problem
In computer architectures, prefetch instructions are ineffective in systems with non-coherent data caches, particularly in image processing applications that handle large numbers of local pixels, due to the non-cacheability of shared memory, leading to increased memory latency and reduced performance.
Innovation Solution
An execution core is configured to receive a prefetch instruction that specifies a memory address, retrieving data from the specified memory address and storing it in a data cache, regardless of whether the data is already present, allowing for continuous prefetching and avoiding cache hits, thus ensuring that old data from previous image captures is ignored.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the execution core checks for cache hits before prefetching data, then memory access is reduced when data is already in cache, but prefetching is ineffective for non-cacheable shared memory in image processing applications
Solution Approach 1:
The execution core performs preliminary prefetching actions for non-cacheable shared memory without checking for cache hits first. This preliminary action ensures that data is fetched from memory into the cache before it is needed by the image processing pipeline, eliminating memory latency without wasting cycles on cache hit checks for non-cacheable memory.
2Reliability
If the execution core always prefetches data from memory regardless of cache status, then prefetching consistency is improved and old data is ignored, but memory bandwidth is consumed even when data is already in cache
Solution Approach 1:
The system applies different prefetching strategies to different memory types: for non-cacheable shared memory used in image processing, the execution core always prefetches data without cache hit checks to ensure data freshness and ignore old data; for other cacheable memory, traditional cache hit checking is maintained to conserve memory bandwidth.
3Reliability
If shared memory is allocated from non-cacheable memory pool to ensure coherence, then data coherence is maintained, but prefetch instructions become ineffective
Solution Approach 1:
The execution core performs preliminary prefetching actions for non-cacheable shared memory without checking for cache hits first. This preliminary action ensures that data is fetched from memory into the cache before it is needed by the image processing pipeline, eliminating memory latency without wasting cycles on cache hit checks for non-cacheable memory.
4Use of energy by moving object
If the execution core checks for cache hits before prefetching, then memory bandwidth is conserved, but stale data from previous image captures may be processed
Solution Approach 1:
The system applies different prefetching strategies to different memory types: for non-cacheable shared memory used in image processing, the execution core always prefetches data without cache hit checks to ensure data freshness and ignore old data; for other cacheable memory, traditional cache hit checking is maintained to conserve memory bandwidth.
Data Source
AI summary
Techniques are disclosed relating to prefetching data from memory. In one embodiment, an integrated circuit may include a processor containing an execution core and a data cache. The execution core may be configured to receive an instance of a prefetch instruction that specifies a memory address from which to retrieve data. In response to the instance of the instruction, the execution core retrieves data from the memory address and stores it in the data in the data cache, regardless of whether the data corresponding to that particular memory address is already stored in the data cache. In this manner, the data cache may be used as a prefetch buffer for data in memory buffers where coherence has not been maintained.