Flash Memory Garbage Collection via Hash Table Cost Indexing
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Solution Overview
Problem
Flash memory devices face performance and reliability issues due to uneven erase cycles, leading to block wear-out and reduced data storage capabilities, as they require efficient garbage collection to manage 'garbage blocks' and maintain performance.
Innovation Solution
A garbage collection method that calculates costs based on multiple factors and uses a hash table to identify blocks with the lowest garbage collection costs for efficient reuse, thereby distributing erase cycles more uniformly across the memory.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If garbage collection is performed frequently to maintain performance, then data storage capability is improved, but block wear-out accelerates due to increased erase cycles
Solution Approach 1:
The patent changes the parameter of garbage collection selection by using a hash table indexed by physical block numbers to identify candidate blocks, rather than arbitrary selection. This systematic approach distributes erase cycles more uniformly across memory blocks, preventing localized wear-out while maintaining data storage capability.
2Productivity
If erase operations are concentrated on specific blocks to free up space quickly, then garbage collection speed is improved, but uniformity of erase distribution deteriorates
Solution Approach 1:
The patent applies local quality by treating different memory blocks differently through the hash table mechanism. Each block's selection for garbage collection is determined by its physical block number hash value, creating a distributed pattern where different regions undergo erasure at different times, ensuring uniform overall distribution while maintaining efficient local garbage collection operations.
3Device complexity
If a simple garbage collection method is used to reduce complexity, then device complexity is reduced, but erase cycle distribution uniformity deteriorates
Solution Approach 1:
The patent implements self-service by using the physical block number itself as the basis for hash table indexing and garbage collection selection. The system automatically distributes erase cycles uniformly without requiring complex external control mechanisms, achieving both low device complexity and high erase distribution uniformity through this self-organizing approach.
Data Source
AI summary
Example embodiments provide a garbage collection method which includes applying a weight to each of at least two or more factors to calculate garbage collection costs. A hash table is configured using the calculated garbage collection costs. The method further includes searching a block having the lowest garbage collection cost from the hash table and performing garbage collection on the searched block.