Cache Line Replacement Status Management via Instruction Fetch Tag Comparison
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Solution Overview
Problem
Current cache management policies struggle to distinguish between repeated accesses and unique accesses of data streams, leading to inefficient eviction and retention of cache lines, which affects processor performance.
Innovation Solution
A method that compares instruction fetch reference tags to maintain or upgrade the cache replacement status of cache lines, differentiating between repeated and unique accesses within an instruction stream, thereby optimizing cache retention and eviction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a cache line is designated as MRU after a single access to distinguish repeated accesses from unique accesses, then cache replacement accuracy is improved, but cache management complexity increases
Solution Approach 1:
The cache line status is segmented into multiple bits: a valid bit indicating whether the cache line contains valid data, and an access count field tracking the number of accesses. This segmentation allows the cache management system to distinguish between single-access and multi-access cache lines without requiring complex management logic, as the segmented status bits automatically provide the differentiation needed for accurate replacement decisions.
2Reliability
If cache lines are retained longer to accommodate data streams accessed once, then data retention accuracy is improved, but cache eviction efficiency deteriorates
Solution Approach 1:
The cache replacement policy dynamically adjusts retention behavior based on the access count field. Cache lines with access count greater than one are retained longer as they represent data streams likely to be accessed again, while cache lines with access count of one are evicted sooner. This dynamic adjustment optimizes both data retention accuracy and eviction efficiency by adapting retention duration to the actual access patterns observed.
3Productivity
If cache replacement status is upgraded only for independently fetched instruction streams, then cache hit rate is improved, but processing overhead increases
Solution Approach 1:
The cache control automatically compares the incoming instruction stream identifier with previously accessed identifiers and updates the access count field accordingly. This self-service mechanism eliminates the need for complex external control logic to track and manage access patterns, as the cache control itself performs the comparison and status update operations, thereby improving cache hit rate while minimizing additional processing overhead.
Data Source
AI summary
A method for managing cache memory including receiving an instruction fetch for an instruction stream in a cache memory, wherein the instruction fetch includes an instruction fetch reference tag for the instruction stream and the instruction stream is at least partially included within a cache line, comparing the instruction fetch reference tag to a previous instruction fetch reference tag, maintaining a cache replacement status of the cache line if the instruction fetch reference tag is the same as the previous instruction fetch reference tag, and upgrading the cache replacement status of the cache line if the instruction fetch reference tag is different from the previous instruction fetch reference tag, whereby the cache replacement status of the cache line is upgraded if the instruction stream is independently fetched more than once. A corresponding system and computer program product.