Memory Controller Read Reclaim Weighting
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Solution Overview
Problem
Existing memory systems face performance deterioration due to excessive frequency of read reclaim operations, which are performed to mitigate read disturb effects in nonvolatile memory devices.
Innovation Solution
A memory controller that manages read counts differently based on the type of read operation (random or sequential) by applying varying weights, allowing for a read reclaim operation to be performed at an appropriate time without excessive frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If read reclaim operation is performed frequently to prevent read disturb, then data reliability is improved, but memory system performance deteriorates
Solution Approach 1:
The patent changes the parameter of read count weighting by distinguishing between sequential read operations (higher weight) and random read operations (lower weight). This allows the read reclaim operation threshold to be triggered more appropriately, preventing excessive read reclaim operations that would degrade performance while still protecting against read disturb effects.
Solution Approach 2:
The patent implements dynamic adjustment of read count accumulation based on read operation types. The controller dynamically determines whether to accumulate read counts for sequential or random read operations, and selectively triggers read reclaim operations based on the accumulated count threshold. This dynamic approach optimizes the balance between data reliability and system performance.
2Stability of the object's composition
If read reclaim operation is performed to mitigate read disturb effect, then threshold voltage stability is improved, but operation frequency increases excessively
Solution Approach 1:
The patent introduces a weighting parameter differentiation between sequential and random read operations. By assigning higher weight to sequential reads and lower weight to random reads, the system changes the effective read count parameter that triggers read reclaim operations, thereby reducing excessive operation frequency while maintaining threshold voltage stability.
Solution Approach 2:
The patent performs preliminary classification of read operations into sequential and random types before accumulating read counts. This preliminary action allows the system to selectively trigger read reclaim operations only when necessary (based on weighted sequential read counts), preventing premature or excessive read reclaim operations that would increase operation frequency unnecessarily.
3Device complexity
If uniform read count management is applied to all read operations, then simplicity is maintained, but read reclaim operations occur at inappropriate times
Solution Approach 1:
The patent changes the read count management parameter by introducing different weights for different read operation types. Instead of uniform counting, the system accumulates weighted read counts where sequential reads have higher weight and random reads have lower weight. This parameter change enables more accurate determination of when read reclaim operations should be performed.
Solution Approach 2:
The patent segments read operations into two distinct categories: sequential read operations and random read operations. By segmenting the read operation types, the system can apply different weighting and accumulation rules to each category, enabling more precise control over read reclaim operation timing while maintaining manageable complexity through clear classification criteria.
Data Source
AI summary
A memory system comprises a memory device including a plurality of memory blocks, and a controller configured to manage a first count, a second count, and a sum value for each of the plurality of memory blocks, the first count being the number of performed random read operations, the second count being the number of performed sequential read operations, the sum value being calculated based on the first count and the second count, and configured to perform a read reclaim operation for a specific memory block among the plurality of memory blocks based on a comparison result of the sum value for the specific block with a reference value.