Bitmap-Guided Valid Data Identification for Garbage Collection
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Solution Overview
Problem
Evaluating an entire logical-to-physical (L2P) table to identify valid data during garbage collection operations in memory systems is inefficient due to the table's large size, leading to significant latency and overhead.
Innovation Solution
Implementing a bitmap for each block of memory cells to indicate relevant subsets of the L2P table, allowing the memory system to efficiently identify valid data by evaluating only these subsets instead of the entire table, with configurable subset sizes to adjust overhead and latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the entire L2P table is evaluated to identify valid data during garbage collection, then complete accuracy in identifying valid data is achieved, but significant latency and overhead occur due to the table's large size
Solution Approach 1:
The L2P table is divided into multiple subsets, each associated with a specific block of memory cells. Instead of evaluating the entire L2P table, the system only evaluates the relevant subset corresponding to the block being garbage collected. This segmentation reduces the evaluation scope from the full table size to a manageable subset size, thereby reducing latency while maintaining complete accuracy in identifying valid data.
2Measurement precision
If the entire L2P table is evaluated to identify valid data during garbage collection, then complete accuracy in identifying valid data is achieved, but processing overhead increases due to the table's large size
Solution Approach 1:
The L2P table is segmented into multiple subsets, where each subset corresponds to a specific block of memory cells. During garbage collection, only the relevant subset is evaluated instead of the entire table. This segmentation reduces processing overhead and complexity by limiting the evaluation scope to only the necessary portion of the table, while still ensuring complete accuracy in valid data identification.
3Loss of time
If subset size is reduced to minimize L2P table evaluation, then latency is reduced, but the number of subsets increases leading to increased bitmap size
Solution Approach 1:
The system dynamically adjusts the subset size and corresponding bitmap configuration based on performance requirements and memory block characteristics. By making the subset size configurable rather than fixed, the system can optimize the balance between latency reduction and bitmap size management, allowing flexible tuning of the garbage collection performance based on specific operational conditions.
Data Source
AI summary
Methods, systems, and devices for valid data identification for garbage collection are described. In connection with writing data to a block of memory cells, a memory system may identify a portion of a logical address space that includes a logical address for the data. The memory system may set a bit of a bitmap, which may indicate that the block includes data having a logical address within a portion of the logical address space corresponding to the bit. The logical address space may be divided into any quantity of portions, each corresponding to a different subset of a logical-to-physical (L2P) table, and the bitmap may include any quantity of corresponding bits. To perform garbage collection on the block, the bitmap may be used to identify one or more subsets of the L2P table to evaluate to determine whether different sets of data within the block are valid or invalid.