Guided Cache Replacement Using Tree Traversal Logic
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Solution Overview
Problem
Conventional cache replacement policies often select non-replaceable cachelines for eviction, leading to inefficient traversal and increased clock cycles, making it difficult to implement in hardware.
Innovation Solution
The introduction of guiding logic that modifies the traversal algorithm to avoid selecting non-replaceable cachelines by evaluating available replaceable cachelines in the tree structure, allowing traversal to proceed in a different direction if no replaceable cachelines are found in the indicated path, thus reducing back traversals and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional cache replacement policies are used to select cachelines for eviction, then the cache replacement process can be implemented, but non-replaceable cachelines are often selected leading to inefficient traversal and increased clock cycles
Solution Approach 1:
The patent applies preliminary action by pre-marking replaceable and non-replaceable cachelines before the replacement process. The guiding logic uses these pre-established markers to quickly identify valid replacement candidates during traversal, avoiding the need to evaluate all cachelines and thus reducing traversal time and clock cycles while maintaining replacement efficiency
Solution Approach 2:
The patent extracts the harmful element (non-replaceable cachelines) from the replacement process by using guiding logic to skip over them. The traversal algorithm is modified to extract or ignore non-replaceable cachelines, focusing only on replaceable ones, thereby eliminating wasted traversal time and improving overall productivity
2Reliability
If the traversal algorithm continuously searches for replaceable cachelines, then valid replacements can be found, but multiple back traversals are required increasing complexity
Solution Approach 1:
The patent introduces guiding logic as an intermediary between the traversal algorithm and the cacheline selection process. This guiding logic uses pre-marked replaceable and non-replaceable indicators to mediate the traversal, directing the algorithm only toward valid replacement candidates and eliminating the need for back traversals, thus reducing complexity while ensuring replacement validity
Solution Approach 2:
The patent segments the cacheline population into replaceable and non-replaceable groups using guiding logic markers. This segmentation allows the traversal algorithm to process only the relevant segment (replaceable cachelines) rather than searching through all cachelines, reducing traversal complexity while maintaining reliable replacement selection
3Reliability
If back traversals are performed to avoid non-replaceable cachelines, then valid replacements are found, but the implementation becomes difficult in hardware
Solution Approach 1:
The patent applies preliminary action by pre-marking replaceable and non-replaceable cachelines before the replacement process. This pre-marking eliminates the need for back traversals during hardware implementation, as the guiding logic can directly navigate to valid candidates using simple forward traversal, making hardware implementation easier while maintaining replacement correctness
Solution Approach 2:
Instead of having the traversal algorithm backtrack when encountering non-replaceable cachelines, the patent inverts the approach by using guiding logic to prevent selection of non-replaceable cachelines in the first place. This inversion eliminates back traversals and simplifies hardware implementation while ensuring correct replacement selection
Data Source
AI summary
Guided cache replacement is described. In accordance with the described techniques, a request to access a cache is received, and a cache replacement policy which controls loading data into the cache is accessed. The cache replacement policy includes a tree structure having nodes corresponding to cachelines of the cache and a traversal algorithm controlling traversal of the tree structure to select one of the cachelines. Traversal of the tree structure is guided using the traversal algorithm to select a cacheline to allocate to the request. The guided traversal modifies at least one decision of the traversal algorithm to avoid selection of a non-replaceable cacheline.