Memory Controller Block Reclaim Search Optimization
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Solution Overview
Problem
In solid-state memory devices, the process of reclaiming blocks for writing new data introduces additional read and write operations, leading to 'write amplification' which reduces the device's lifetime and endurance, and existing methods for identifying blocks for erasure are inefficient, especially in large systems where frequent updates require substantial CPU cycles.
Innovation Solution
A method is introduced where data updates are written to a subunit different from the outdated data, and a memory controller searches for a unit that matches a predetermined criterion to identify blocks for erasure, stopping the search once a suitable block is found, and rewriting valid subunits from the identified block to other blocks, thereby reducing CPU cycles and maintaining low write amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a search is performed amongst all units to identify a unit matching a predetermined criterion for block reclaiming, then the precision of block selection is improved, but the CPU cycles and time required increase substantially
Solution Approach 1:
The patent applies partial action by performing a limited search through units rather than exhaustively searching all units. The search stops when a unit matching the predetermined criterion is found, or when a predefined limit is reached, thus performing only the necessary portion of the search to achieve adequate block selection without wasting CPU cycles on unnecessary examinations of all units.
Solution Approach 2:
The patent segments the search process into discrete steps where units are examined sequentially until a match is found. This segmentation allows the system to break down the exhaustive search into manageable portions, stopping early when sufficient information is obtained, thereby reducing overall CPU cycle consumption while maintaining acceptable selection precision.
2Productivity
If additional read and write operations are performed during block reclaiming, then blocks can be freed for new writes, but write amplification increases which reduces device lifetime and endurance
Solution Approach 1:
The patent changes the parameter of search termination by introducing a stop condition that limits the number of units examined. This parameter change reduces the total number of read operations required during block reclaiming, thereby reducing write amplification and extending device lifetime while still achieving effective block reclamation through the units that are examined.
Solution Approach 2:
The system uses the predetermined criterion and automatic stop condition to self-regulate the reclaiming process, preventing excessive read and write operations. This self-service mechanism ensures that block reclamation is performed efficiently without causing harmful write amplification that would reduce device endurance.
3Measurement precision
If the search for a matching unit continues until all units are examined, then the optimal block for erasure is identified, but the implementation complexity and processing overhead increase
Solution Approach 1:
The patent applies partial action by examining only a subset of units rather than all units. The search is terminated early when a unit matching the criterion is found or when a predefined limit is reached, reducing processing overhead and implementation complexity while maintaining sufficient block identification accuracy for effective reclamation.
Data Source
AI summary
A method and apparatus for managing write operations in memory. The method includes a memory including units, each of the units including subunits. Data updates are written “out-of-place”, in that new data does not overwrite the memory locations (subunits) where the data is currently stored. The at least one subunit containing the outdated data is marked as invalid. As a result, a subunit can contain up to date data in a valid subunit next to invalid subunits. For reclaiming units for erasure, it is searched amongst the units to identify a unit or units that match a predetermined criterion. The data of valid subunits of such identified unit is rewritten to another unit or units.