L2P Table Compression via MSB Prefix Segmentation
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Solution Overview
Problem
As solid-state drives (SSDs) increase in capacity, their physical addresses require more bits to represent, leading to large storage needs for address indirection tables, which results in increased power consumption and access time due to long addresses exceeding burst lengths, necessitating a method to compress physical addresses for efficient memory access.
Innovation Solution
The method involves identifying most significant bits (MSBs) and least significant bits (LSBs) of physical addresses, storing MSBs jointly as data bits, and storing LSBs separately, allowing for compression and reduced storage space in the address indirection table, enabling multiple addresses to be packed into a 64-byte codeword accessible via burst reads/writes, thus reducing DRAM access latency and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If physical addresses are stored with full length to ensure unique addressing, then addressing capability is improved, but storage space requirement increases
Solution Approach 1:
The physical address is divided into two segments: common prefix bits (stored once in the first entry) and unique suffix bits (stored in each subsequent entry). This segmentation allows the L2P table to store full physical addresses implicitly while explicitly storing only the varying parts, significantly reducing storage space while maintaining complete addressing capability.
Solution Approach 2:
The L2P table entries are nested with the first entry containing the common prefix and subsequent entries containing only the unique suffixes. This nested structure allows the system to store hierarchical address information where the outer layer (first entry) contains shared data and inner layers (subsequent entries) contain specific variations, optimizing storage efficiency.
2Quantity of substance
If physical addresses are compressed to reduce storage space, then storage efficiency is improved, but address retrieval complexity increases
Solution Approach 1:
The common prefix of physical addresses is pre-computed and stored in the first L2P table entry before any address translation operations occur. This preliminary action eliminates the need for repeated prefix extraction during address translation, reducing retrieval complexity while maintaining compression benefits.
Solution Approach 2:
The L2P table structure acts as an intermediary between logical addresses and full physical addresses. Instead of directly storing or computing complete physical addresses for each logical address mapping, the system uses the compressed L2P table format with prefix-suffix structure as an intermediate representation, simplifying the overall address translation process.
3Adaptability or versatility
If address indirection table size increases to accommodate more addresses, then addressing coverage is improved, but access time increases
Solution Approach 1:
By segmenting physical addresses into common prefixes and unique suffixes, the L2P table reduces the effective storage size of each address entry. This segmentation allows the table to fit more address mappings within the same memory capacity, improving addressing coverage while maintaining fast access times due to the reduced entry size.
Data Source
AI summary
This application is directed to compressing a logical-to-physical (L2P) address indirection table in a memory system of an electronic device. The electronic device determines a plurality of physical addresses corresponding to an ordered sequence of logical addresses. Each logical address corresponds to a distinct physical address. The electronic device identifies a set of most significant bits (MSBs) and a set of least significant bits (LSBs) of each of the plurality of physical addresses and determines a set of data bits based on a plurality of MSB sets including the set of MSBs of each of the plurality of physical addresses. The set of LSBs of each of the plurality of physical addresses and the set of data bits are stored jointly in the L2P address indirection table.