Banked L2P Garbage Collection for Fragmented Memory Blocks
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Solution Overview
Problem
Existing memory systems face inefficiencies in garbage collection processes, leading to reduced write capacity due to fragmented data storage and increased access loads on the L2P table, necessitating the use of a P2L table that consumes nonvolatile memory resources.
Innovation Solution
The memory system divides the logical address space into banks and associates blocks with these banks, allowing selective scanning within a single bank during garbage collection, reducing the scan range and minimizing access to the L2P table, thereby improving write amplification and defragmenting fragmented data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the memory controller scans the entire L2P table during garbage collection, then all valid data can be found, but the access load on the L2P table increases and write amplification worsens
Solution Approach 1:
The patent segments the L2P table into multiple banks corresponding to different address spaces. During garbage collection, the memory controller scans only the L2P table entries associated with the specific bank containing the target block, rather than scanning the entire table. This segmentation reduces the scan range and minimizes access load on the L2P table while still ensuring complete data recovery within the relevant scope.
2Productivity
If the memory controller uses a P2L table to track physical addresses, then write capacity is maintained, but nonvolatile memory resources are consumed
Solution Approach 1:
The patent makes the L2P table serve multiple functions: it not only maps logical addresses to physical addresses for normal data access but also utilizes it for garbage collection operations. By scanning L2P table entries during garbage collection, the system eliminates the need for a separate P2L table, thereby maintaining write capacity while avoiding the additional nonvolatile memory consumption that would be required for a dedicated P2L table.
3Productivity
If the memory controller performs garbage collection on fragmented data, then writeable memory area is maintained, but the scan range increases
Solution Approach 1:
The patent divides the address space into multiple banks, each with its own L2P table entries. When garbage collection is needed for a specific block, the memory controller identifies which bank contains the block and scans only the L2P table entries for that bank. This segmentation approach significantly reduces the scan range compared to scanning the entire L2P table, while still enabling effective garbage collection of fragmented data to maintain writeable memory area.
Data Source
AI summary
According to one embodiment, a memory system includes: a nonvolatile memory including blocks each of which includes physical memory areas; and a memory controller dividing a logical address space into a plurality of banks and associating a block with each of the plurality of banks. The memory controller is configured to: selectively scan a portion related to a first bank among the plurality of banks in a table in which a physical address corresponding to a physical memory area in which valid data is stored is mapped on the logical address space; detect a first physical address corresponding to a first physical memory area in a first block associated with the first bank as a result of the scan; read first valid data stored in the first block based on the first physical address; and write the first valid data in a second block associated with the first bank.