Flash Memory Controller SRAM Caching for L2P Mapping
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Solution Overview
Problem
The frequent cache invalidation in flash memory controllers due to the large size of the logical-to-physical (L2P) mapping table, which leads to significant deterioration in read/write performance, as only a portion of the table is loaded into DRAM and frequent loading results in lengthy cache invalidation times.
Innovation Solution
Loading the required groups of the L2P mapping table into static random access memory (SRAM) instead of dynamic random access memory (DRAM), allowing the flash memory controller to directly access SRAM for address mapping, thereby reducing cache invalidation time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the L2P mapping table is loaded into DRAM for handling host read/write commands, then the flash memory controller can process commands, but the cache invalidation time increases significantly due to frequent loading requirements
Solution Approach 1:
The patent introduces SRAM as an intermediary memory component between the DRAM and the L2P mapping table. The SRAM cache stores frequently accessed mapping information, acting as a mediator that reduces the frequency of cache invalidations by providing a faster access layer for commonly needed mapping data, thereby resolving the contradiction between processing capability and time loss.
Solution Approach 2:
The patent implements preliminary loading of L2P mapping table groups into the SRAM cache before they are actually needed for host commands. By anticipating and pre-loading mapping information into the SRAM cache, the system avoids frequent cache invalidations when commands arrive, thus improving read/write performance while reducing time loss from cache invalidation.
2Quantity of substance
If only a portion of the L2P mapping table is loaded to DRAM at a time, then the limited DRAM capacity is respected, but frequent cache invalidation occurs when handling random read/write commands
Solution Approach 1:
The patent segments the L2P mapping table into multiple groups that can be independently managed. Instead of loading the entire table into DRAM, the system divides it into manageable portions and uses the SRAM cache to store frequently accessed segments. This segmentation allows the system to respect DRAM capacity limits while improving cache validity by keeping relevant mapping information in the faster SRAM cache.
Solution Approach 2:
The patent applies local quality by differentiating the storage characteristics of different memory components: DRAM is used for bulk storage with limited capacity, while SRAM cache is used for frequently accessed local mapping information. This creates a hierarchical memory structure where different parts of the mapping table have different quality characteristics in terms of access speed and validity, resolving the contradiction between capacity utilization and cache validity.
3Adaptability or versatility
If the L2P mapping table is frequently reloaded to handle random read/write commands, then the mapping information is updated, but the read/write performance is significantly deteriorated
Solution Approach 1:
The SRAM cache acts as an intermediary layer that stores mapping information for random read/write commands. Instead of frequently reloading the entire L2P mapping table into DRAM, the system maintains a cached copy in SRAM that can be quickly accessed. This intermediary structure allows the system to adapt to random commands while maintaining high read/write performance by avoiding frequent reloads.
Solution Approach 2:
The system performs preliminary action by pre-loading and caching mapping information in the SRAM cache before random read/write commands arrive. This anticipation of future needs allows the system to handle random commands efficiently without the performance deterioration that would result from frequent reloading of the complete mapping table.
Data Source
AI summary
A method of caching mapping table for use in a flash memory device having a flash memory controller and a flash memory is provided. The method includes: in response to a host read command, determining whether a group of a logical-to-physical (L2P) required by handling the host read command has been loaded to a DRAM of the flash memory controller; if the required group of the L2P mapping table has not been loaded to the DRAM, loading the required group of the L2P mapping table from the flash memory to a SRAM of the flash memory controller; directly accessing the SRAM to obtain an L2P address associated with the host read command from the required group of the L2P mapping table; and performing a read operation on the flash memory in response to the host read command according to the obtained L2P address.