NAND Controller Dynamic Read Command Delay for Parallel Execution
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Solution Overview
Problem
Current NAND memory devices often fail to maximize the probability of parallel execution of read commands across different portions of a single die, leading to suboptimal read throughput due to the requirement of multiple commands targeting the same die simultaneously, which is rare in certain workloads.
Innovation Solution
Introducing a delay mechanism for issuing read commands to increase the likelihood of multi-plane read execution, where if no other eligible read commands are present, the controller delays the command issuance until a compatible second read command is received or the delay period expires, allowing for simultaneous execution of multiple read commands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If read commands are issued immediately without delay, then single-command latency is minimized, but the probability of parallel execution across different portions of the die is reduced
Solution Approach 1:
The controller delays issuing the first read command for a predetermined time period before actual execution. This preliminary delay allows time for a second read command to be received, enabling both commands to be executed in parallel across different portions of the die, thereby increasing read throughput while accepting a slight increase in single-command latency
2Productivity
If multiple read commands are executed in parallel, then read throughput is increased, but system complexity increases due to command queue management and timing coordination
Solution Approach 1:
The die is divided into different portions (e.g., planes or command queues) that can independently execute read commands. By segmenting the memory structure and associating different command queues with different portions, the system enables parallel execution while maintaining manageable complexity through modular organization
Solution Approach 2:
The controller dynamically determines whether to delay or immediately execute read commands based on real-time conditions such as whether a second command is received within the delay period. This dynamic adaptation allows the system to optimize for parallel execution when possible while falling back to immediate execution when not, balancing throughput gains against latency costs
Data Source
AI summary
Disclosed in some examples are methods, systems, memory devices, and machine-readable mediums which increase read throughput by introducing a delay prior to issuing a command to increase the chances that read commands can be executed in parallel. Upon receipt of a read command, if there are no other read commands in the command queue for a given portion (e.g., plane or plane group) of the die, the controller can delay issuing the read command for a delay period using a timer. If, during the delay period, an eligible read command is received, the delayed command and the newly received command are both issued in parallel using a multi-plane read. If no eligible read command is received during the delay period, the read command is issued after the delay period expires.