Virtual Block Garbage Collection Using Hot-Cold Data Separation
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Solution Overview
Problem
Memory systems face inefficiencies in garbage collection due to the inability to accurately determine usage levels of virtual blocks, leading to increased maintenance operations, reduced read and write performance, and higher write amplification.
Innovation Solution
The memory system tracks usage levels of virtual blocks by utilizing an unused spare page area in a mapping table to maintain counters for logical block addresses, incrementing them based on access frequency, and adjusts garbage collection procedures accordingly to separate hot and cold data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional garbage collection is performed on all virtual blocks without differentiation, then memory maintenance is ensured, but write amplification increases and performance decreases
Solution Approach 1:
The patent segments virtual blocks into different categories based on their usage characteristics (hot, cold, dead blocks) and applies differentiated garbage collection strategies to each segment. This allows the system to perform intensive GC only on cold blocks while avoiding or reducing GC on hot blocks, thereby reducing overall write amplification while maintaining necessary memory maintenance.
Solution Approach 2:
The patent implements local quality by applying different garbage collection policies to different regions of the storage system based on their specific characteristics. Hot blocks receive minimal or no GC operations, cold blocks receive standard GC, and dead blocks receive aggressive GC, optimizing the balance between maintenance and performance for each local region.
2Reliability
If frequent garbage collection is performed to maintain memory efficiency, then valid data is preserved, but read and write performance are reduced
Solution Approach 1:
The patent implements dynamic garbage collection by continuously monitoring block usage characteristics and adjusting GC frequency and intensity accordingly. Blocks are re-evaluated over time, allowing the system to adapt GC strategies as blocks transition between hot, cold, and dead states, thereby maintaining valid data while minimizing performance impact.
Solution Approach 2:
The system employs feedback mechanisms by tracking usage patterns of virtual blocks and using this information to dynamically adjust garbage collection policies. The feedback loop monitors block characteristics and modifies GC behavior to preserve valid data while optimizing performance based on actual usage conditions.
3Device complexity
If garbage collection is performed without usage level differentiation, then memory maintenance is simplified, but maintenance operation frequency increases
Solution Approach 1:
The patent applies preliminary action by pre-classifying virtual blocks into usage categories (hot, cold, dead) based on their access patterns before garbage collection is performed. This pre-characterization allows the system to quickly determine appropriate GC strategies without complex real-time analysis during GC operations, reducing maintenance frequency while maintaining necessary complexity for optimization.
Data Source
AI summary
Methods, systems, and devices for garbage collection based on data characteristics are described. A memory system may receive a write command associated with a first logical block address (LBA) of a virtual block of the memory system, where the virtual block may be associated with a first value indicating a version of the virtual block. The memory system may adjust a value of a first counter within a mapping table in response to a difference between the first value and a second value satisfying a first threshold value. The second value may indicate a quantity of opened virtual blocks. The memory system may determine whether the value of the first counter satisfies a second threshold value, and transfer as part of garbage collection, data associated with the virtual block to a second virtual block in response to the value of the first counter satisfying the second threshold value.