Persistent Memory Data Migration via Logical Address Translation
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Solution Overview
Problem
The existing data migration process from persistent memory to external storage devices involves excessive access to the memory controller, leading to bandwidth inefficiencies due to the need to read data into RAM and construct scatter gather lists based on physical addresses, which increases the number of operations on the memory controller.
Innovation Solution
A method and apparatus that calculate the physical address of data directly from its logical address, allowing for the construction of scatter gather lists without the need to read data into RAM, thereby reducing the number of operations on the memory controller and enhancing bandwidth efficiency by directly instructing the DMA engine to migrate data between internal and external storage devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If data is read from persistent memory to RAM and scatter gather list is constructed based on physical address in RAM, then the DMA engine can read data from RAM, but the memory controller is accessed three times which greatly affects bandwidth
Solution Approach 1:
The patent extracts the unnecessary intermediate step of copying data to RAM. By directly constructing the scatter gather list using physical addresses from persistent memory, the method removes the redundant memory controller access to RAM, reducing the access count from three times to two times (persistent memory read and external storage write), thereby preserving bandwidth.
Solution Approach 2:
The patent performs preliminary address translation and scatter gather list construction using logical addresses directly from the persistent memory without first loading data into RAM. This preliminary action eliminates the need for subsequent RAM operations and reduces memory controller access frequency.
2Ease of operation
If data is read into RAM before constructing scatter gather list, then the physical address can be obtained, but the number of operations on memory controller increases
Solution Approach 1:
The patent makes the persistent memory serve multiple functions simultaneously: it acts as both the source data storage and provides the physical addresses directly for scatter gather list construction. This eliminates the need for a separate RAM component for address extraction, reducing overall system complexity and memory controller operations.
3Reliability
If the memory controller is accessed three times in data transmission procedure, then data can be migrated from persistent memory to external storage, but bandwidth of memory controller is greatly affected
Solution Approach 1:
The patent enables continuous data migration operations by reducing memory controller access interruptions. By eliminating the intermediate RAM copy step, the memory controller maintains continuous useful action on persistent memory without being repeatedly accessed for intermediate storage operations, thereby improving effective bandwidth and migration speed.
Data Source
AI summary
A data migration method is disclosed, including: determining a first address of target data that is to be migrated from an internal storage device to an external storage device, the first address is a logical address of the internal storage device; calculating a physical address of the target data in the internal storage device based on the first address; constructing a scatter gather list, where the scatter gather list includes the physical address of the target data in the internal storage device; sending a migration instruction to a direct memory access engine.