Eviction Control Circuitry for Storage Structure Access
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Solution Overview
Problem
Existing data processing systems face inefficiencies in eviction policies due to over-promotion of entries caused by repeated accesses, leading to distorted eviction control information and reduced effectiveness in maintaining relevant data in storage structures.
Innovation Solution
The implementation of eviction control circuitry that maintains an indication of the most-recent entry for each group, preventing updates to the eviction control information when the most-recent entry is accessed, thereby avoiding over-promotion and ensuring that sequential accesses are logically treated as a single access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If eviction control information is updated in response to every access to an entry, then the eviction policy can accurately track access patterns, but repeated accesses to the same entry cause over-promotion and distort the eviction control information
Solution Approach 1:
The patent extracts the problematic repeated updates from the eviction control information by introducing a separate most-recent-entry indicator. This indicator captures the essence of repeated accesses without allowing them to distort the eviction control information, effectively separating the tracking function from the eviction decision function.
Solution Approach 2:
The most-recent-entry indicator serves as an intermediary between the access pattern and the eviction control information. It mediates the effect of repeated accesses by identifying them and preventing their distortion impact from reaching the eviction control information, while still allowing the system to recognize and handle repeated accesses appropriately.
2Productivity
If the system tracks access patterns for every entry, then eviction decisions can be optimized, but the complexity of maintaining eviction control information increases
Solution Approach 1:
The patent extracts the complex tracking of access patterns from the eviction control information by separating it into a simple most-recent-entry indicator. This reduces the complexity of maintaining eviction control information while preserving the ability to make optimized eviction decisions based on access patterns.
Solution Approach 2:
The patent applies local quality by treating each entry's access pattern tracking differently through the most-recent-entry indicator. Instead of uniformly tracking all accesses, it locally identifies only the most recent entry, simplifying the overall system while maintaining local accuracy for eviction decisions.
3Measurement precision
If sequential accesses are treated as multiple independent accesses, then access frequency is accurately reflected, but entries are unnecessarily retained due to over-promotion
Solution Approach 1:
The most-recent-entry indicator acts as an intermediary that recognizes sequential accesses to the same entry and prevents them from being counted as multiple independent accesses. This mediator allows the system to maintain accurate access frequency measurement for different entries while preventing over-promotion of the same entry accessed sequentially.
Solution Approach 2:
Instead of counting each access to an entry, the patent inverts the approach by tracking which entry was most recently accessed and preventing updates for that entry. This inversion transforms the problem from counting accesses to recognizing and excluding repeated accesses, thereby preventing over-promotion while maintaining measurement accuracy.
Data Source
AI summary
A technique is provided for controlling eviction from a storage structure. An apparatus has a storage structure with a plurality of entries to store data. The apparatus also has eviction control circuitry configured to maintain eviction control information in accordance with an eviction policy, the eviction policy specifying how the eviction control information is to be updated in response to accesses to the entries of the storage structure. The eviction control circuitry is responsive to a victim selection event to employ the eviction policy to select, with reference to the eviction control information, one of the entries to be a victim entry whose data is to be discarded from the storage structure. The eviction control circuitry is further configured to maintain, for each of one or more groups of entries in the storage structure, an indication of a most-recent entry. The most-recent entry is an entry in that group that was most recently subjected to at least a given type of access. For each group, in response to an access to a given entry of that group other than the most-recent entry for that group, the eviction control circuitry is configured to update the eviction control information according to the eviction policy. However, in response to an access to the most-recent entry for that group, the eviction control circuitry is configured to prevent an update to at least the eviction control information associated with the most-recent entry.