NAND L2P Region Tracking via Bitmap for Garbage Collection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional NAND flash memory devices face inefficiencies in garbage collection due to the need to search and load entire logical-to-physical (L2P) tables from slower NAND storage into working memory, leading to high latencies and wasted time when no physical pages are found in the block, especially when the table is larger than the working memory.
Innovation Solution
Implementing a data structure, such as a bitmap, that tracks which L2P table regions are pertinent to a given block, allowing only those regions to be loaded into working memory during garbage collection, reducing the number of regions and increasing search efficiency by indicating valid pages and maintaining the structure during writes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the entire L2P table is loaded into working memory during garbage collection, then complete mapping information is available for search, but the time required to load and search the table increases significantly
Solution Approach 1:
The L2P table is divided into multiple regions, and a bitmap data structure is used to track which regions contain valid pages for each block. During garbage collection, only the relevant regions indicated by the bitmap are loaded into working memory, rather than loading the entire table. This segmentation approach maintains search completeness for the relevant block while significantly reducing the time and memory required.
Solution Approach 2:
The bitmap data structure extracts and stores only the essential information about which L2P regions are pertinent to each block. This extracted information allows the system to selectively load only the necessary table regions into working memory during garbage collection, eliminating the need to load and search irrelevant regions, thus reducing latency while maintaining search effectiveness.
2Productivity
If L2P table regions are selectively loaded based on a tracking data structure, then garbage collection efficiency improves, but additional maintenance overhead is introduced
Solution Approach 1:
The bitmap data structure is automatically updated during normal write operations to the NAND device. When pages are written to a block, the corresponding L2P region bits in the bitmap are set to indicate validity. This self-updating mechanism ensures the tracking structure remains current without requiring separate maintenance operations, balancing the efficiency gains with minimal additional complexity.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Devices and techniques for NAND logical-to-physical table region tracking are described herein. A write request, including a logical page and data to be written at the logical page, is received at a controller of a NAND device. The NAND controller may then establish an entry in a logical-to-physical (L2P) mapping table between the logical page and a physical page of a physical block of the NAND device to which the data is written. Here, the entry may be in a region of the L2P mapping table that is one of multiple regions. An indication of the region may be written in a data structure corresponding to the physical block.