Memory Controller Wear Level Tracking via Hierarchical Access Logging
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Solution Overview
Problem
In memory systems with nonvolatile memory, managing the wear level is challenging due to the need for precise tracking of access numbers, which is complicated by the varying access granularity between different memory types, leading to either excessive management information or errors in wear estimation.
Innovation Solution
The memory system divides the storage area into multiple areas and uses an access number table to manage total accesses, while an address log tracks current accesses in finer sub-areas, updating counts only when duplicate accesses occur, thereby improving measurement precision and reducing management table volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If access information is recorded for every access to each sub area, then measurement precision of wear level is improved, but management table volume increases excessively
Solution Approach 1:
The patent extracts only the necessary access information (duplicate accesses) from the complete access log. Instead of recording all accesses, it selectively records only duplicate accesses to sub areas, thereby reducing management table volume while maintaining sufficient precision for wear level measurement.
Solution Approach 2:
The patent applies partial action by recording access information only when duplicate accesses occur, rather than recording every single access. This partial recording strategy reduces the volume of management tables while still providing accurate enough data for wear level assessment.
2Measurement precision
If access granularity is made fine to track individual sub area accesses, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the storage area into multiple areas, each containing multiple sub areas. This hierarchical segmentation allows for fine-grained tracking of sub area accesses while managing complexity through structured organization. The access number table is also segmented to store information per area rather than per individual sub area.
Solution Approach 2:
The patent merges the tracking of multiple sub area accesses into a single access number table entry per area. By combining sub area level information into area-level summaries, it reduces device complexity while maintaining the ability to track fine-grained access patterns through the hierarchical structure.
3Reliability
If all access numbers are updated for each access, then reliability of wear estimation is improved, but productivity of write operations decreases
Solution Approach 1:
The patent implements periodic updating of access numbers, where updates occur only when duplicate accesses are detected rather than continuously with every access. This periodic update mechanism maintains reliable wear estimation by capturing meaningful access patterns while reducing the frequency of update operations to improve write performance.
Solution Approach 2:
The patent extracts and updates only the necessary access number information when duplicate accesses occur, rather than updating all access numbers with every single access. This selective update approach maintains wear estimation reliability by tracking duplicate patterns while minimizing the overhead of update operations.
Data Source
AI summary
According to one embodiment, for each area having a first size, a number of accesses to the area is recorded in first information. In units of sub areas each having a second size smaller than the first size, access information for the sub area is recorded in the second information. In the first information, the number of accesses to an area to which a sub area in which duplicate accesses occur belongs is updated.