Flash Memory Read-Ahead Buffering for Low Queue Depth Reads
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Solution Overview
Problem
The existing flash memory reading mechanisms face limitations due to a low command queue depth, which restricts the ability to handle multiple commands simultaneously, thereby underutilizing interleaving architectures.
Innovation Solution
Implement a read-ahead operation in the memory controller to predict sequential read access and store data in a buffer, allowing the controller to send data from the buffer instead of re-reading from the flash memory when subsequent commands match the buffered data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If interleaving architecture is used to increase read performance, then parallel access capability is improved, but command queue depth remains low limiting full utilization
Solution Approach 1:
The patent implements a read-ahead mechanism that proactively reads data from flash memory into a buffer before the host actually requests it. The controller predicts sequential access patterns and pre-loads data into an internal buffer, so when the host issues read commands, data is already available in the buffer ready for immediate transmission. This preliminary action resolves the contradiction by decoupling the actual read operations from host commands, enabling the interleaved channels to work continuously on pre-fetching data while the host simply consumes from the buffer.
2Productivity
If command queue depth is increased to handle more commands simultaneously, then command handling capacity is improved, but system complexity increases
Solution Approach 1:
The patent introduces an internal buffer as an intermediary layer between the flash memory and the host. This buffer acts as a mediator that absorbs the complexity of managing deep command queues and interleaved channel operations. The buffer stores pre-read data and serves it to the host on demand, effectively decoupling the complex memory management operations from the simple host interface. This intermediary approach enables high command handling capacity without requiring the host to manage complex queue structures.
Data Source
AI summary
A method for reading data from a flash memory is provided. The method comprises: determining whether a host device is requesting a sequential read access to the flash memory; prior to receiving a first host read command issued by the host device, performing a read-ahead operation to read data from the flash memory according to a read-ahead start logical block address (LBA) if the host device is requesting the sequential read access to the flash memory; and storing the data that is read through the read-ahead operation in a read-ahead buffer; and in response to receiving a first host read command issued by the host device, sending a portion or all of data that is read through the read-ahead operation to the host device if a start LBA of the first host read command corresponds to one of start LBAs of data that is stored in the read-ahead buffer.