IOMMU-Guided Memory Page Migration for Legacy IO Access
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Solution Overview
Problem
Electronic devices face inefficiencies in accessing data stored in memory due to the use of different types of memory with varying access speeds, leading to potential crashes or errors when older IO devices lack support for migrating pages of memory during relocation.
Innovation Solution
Implement a page migration engine and an IOMMU to manage memory access and migration, using IO page tables and a reverse map table to ensure IO devices do not access migrating pages, thereby preventing errors and optimizing memory location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pages of memory are migrated automatically behind the scenes without IO device knowledge, then memory access efficiency is improved through optimal data placement, but system reliability deteriorates when older IO devices lack support for migrating pages during relocation
Solution Approach 1:
The system performs preliminary actions by checking whether an IO device supports page migration before initiating migration of pages that the device needs. This prevents attempting to migrate pages to devices that cannot handle the operation, thereby avoiding crashes and errors while maintaining efficient memory placement for supported devices
Solution Approach 2:
The page migration engine acts as an intermediary between the memory management system and IO devices. It manages the migration process by identifying supported devices, coordinating migration operations, and ensuring that only pages are migrated to devices capable of handling the operation, thus resolving the contradiction between automation and reliability
2Extent of automation
If pages of memory are migrated without IO device support, then memory relocation can proceed automatically, but device complexity increases due to need for migration management mechanisms
Solution Approach 1:
The system implements self-service by having the page migration engine automatically identify which IO devices support page migration and autonomously manage the migration process for supported devices. This automation reduces the need for manual intervention while the engine handles the complexity of migration coordination
Solution Approach 2:
The page migration engine serves as an intermediary layer that handles the complexity of migration management. It abstracts the migration details from the memory management system and IO devices, providing a simplified interface that enables automatic migration while managing the underlying complexity through centralized coordination
Data Source
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AI summary
An electronic device includes a memory, a processor that executes a software entity, a page migration engine (PME), and an input-output memory management unit (IOMMU). The software entity and the PME perform operations for preparing to migrate a page of memory accessible by at least one IO device in the memory, the software entity and the PME setting migration state information in a page table entry for the page of memory and information in reverse map table (RMT) entries involved with migrating the page of memory based on the operations being performed. The IOMMU controls usage of information from the page table entry and controls performance of memory accesses of the page of memory based on the migration state information in the page table entry and information in the RMT entries. The PME migrates the page of memory upon completing the operations for preparing to migrate the page of memory.