Pinned Memory Migration via Dualcast Writes During DMA
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Solution Overview
Problem
Existing systems face inefficiencies and delays due to the inability to migrate pinned memory pages during ongoing I/O operations, leading to issues such as I/O fabric back-pressure, system-wide timeouts, and memory fragmentation, which impact cloud, edge, and client systems.
Innovation Solution
A system architecture and techniques enable the migration of pinned memory pages by using Pinned Memory Migration (PMM) logic to perform a 'Dualcast' operation, ensuring write operations are observed in both source and destination pages, and employing a Transactional Memory Copy to maintain data consistency during migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If memory pages are pinned to ensure data correctness during I/O operations, then data correctness is improved, but memory migration capability deteriorates
Solution Approach 1:
The patent segments the memory access path by introducing a memory copy engine that creates parallel copy paths. The pinned memory page is divided into source and destination regions, with the copy engine creating independent copy channels that bypass the pinning restriction, allowing migration while maintaining data integrity through coordinated access control.
Solution Approach 2:
The memory copy engine acts as an intermediary component between the pinned memory page and the migration process. It mediates the copy operation by intercepting access requests, managing the dual cast mechanism, and coordinating with the I/O device to ensure data correctness is maintained during migration without requiring traditional pinning restrictions.
2Adaptability or versatility
If DMA operations are paused to migrate pinned memory pages, then memory migration is enabled, but system performance deteriorates
Solution Approach 1:
The patent enables continuous DMA operations during memory migration by implementing a dual cast mechanism. The memory copy engine maintains active DMA transfers to the source memory page while simultaneously copying data to the destination page, eliminating the need to pause DMA operations and ensuring continuous useful action throughout the migration process.
Solution Approach 2:
The system performs preliminary setup by configuring the memory copy engine with source and destination address mappings before migration begins. The dual cast paths are pre-established and coordinated with the I/O device, allowing migration to proceed without interrupting ongoing DMA operations, thus maintaining system performance.
3Reliability
If pinned memory pages cannot be migrated, then data correctness is maintained, but memory fragmentation increases
Solution Approach 1:
The memory copy engine segments the migration process into controlled copy operations that maintain data correctness. By dividing the pinned memory page into manageable copy regions and using coordinated dual cast mechanisms, the system enables migration while preserving data integrity, thereby reducing memory fragmentation without compromising reliability.
Data Source
AI summary
Methods and apparatus relating to a system architecture and techniques for pinned memory migration are described. In an embodiment, one or more memory devices store a source page and a destination page. Logic circuitry causes a write operation from an Input/Output (I/O) device to be observed for both the source page and the destination page. A transactional memory copy operation is to be performed from the source page to the destination page. Other embodiments are also disclosed and claimed.