Progressive Program Suspend Resume for NAND Read Latency
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Solution Overview
Problem
NAND memory devices experience high read QoS latency due to exhaustion of program suspend commands during heavy read-intensive workloads, leading to prolonged wait times for read requests as program operations are not completed until finished.
Innovation Solution
Implementing Progressive Program Suspend Resume (PPSR) technology, which divides the programming sequence into multiple tiers based on suspend count and modulates forward progress, allowing for configurable suspend points to prioritize read operations and prevent exhaustion of suspend commands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If program suspend commands are enabled to prioritize read operations, then read QoS latency is improved, but suspend commands are exhausted quickly during heavy read-intensive workloads
Solution Approach 1:
The patent segments the program operation into multiple tiers based on threshold voltages (first tier: lower threshold voltages, second tier: higher threshold voltages). This segmentation allows different suspend/resume behaviors in different tiers, enabling the system to allow more suspends in the first tier while limiting suspends in the second tier, thus preventing suspend exhaustion while maintaining read performance.
Solution Approach 2:
The patent implements dynamic suspend/resume control where the ability to suspend is adjusted based on the current tier and workload conditions. The system dynamically transitions between tiers based on program progress and can selectively allow or disallow suspends in different tiers, creating a dynamic response to read requests that adapts to current system state.
2Loss of time
If program operation is suspended frequently to service read requests, then read latency is reduced, but program operation progress is delayed
Solution Approach 1:
By dividing the program operation into tiers with different suspend policies, the patent ensures that program progress continues in the second tier even when read requests occur, while the first tier remains suspendable. This segmentation balances read serviceability with program progress across different voltage ranges.
Solution Approach 2:
The patent applies different quality characteristics to different parts of the program operation: the first tier (lower voltages) is made more suspendable to service reads, while the second tier (higher voltages) is made less suspendable to ensure progress. This local differentiation optimizes both read latency and program speed in their respective regions.
Data Source
AI summary
Systems, apparatuses and methods may provide for technology that resumes a program operation with respect to NAND memory during a first tier in response to a suspension counter reaching a first threshold and resumes the program operation with respect to the NAND memory during a second tier in response to the suspension counter reaching a second threshold. The technology may also resume the program operation with respect to the NAND memory during a third tier in response to the suspension counter reaching a third threshold. Additionally, the technology may service one or more read operations with respect to the NAND memory until the suspension counter reaches the first threshold during the first tier, until the suspension counter reaches the second threshold during the second tier, and until the suspension counter reaches the third threshold during the third tier.