IOMMU Page Migration Control for IO-Accessible Memory
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Solution Overview
Problem
Existing electronic devices face inefficiencies in data access due to improper storage of high-priority or time-critical data in slower memory types, and IO devices lack support for migrating memory pages, leading to potential crashes or errors during migration.
Innovation Solution
Implement a page migration engine and IOMMU to manage memory access and migration, using page table entries with migration state information to control IO device access, ensuring seamless migration of memory pages without crashes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If automatic migration mechanisms migrate pages of memory behind the scenes without communicating with accessing entities, then migration overhead is reduced and performance is improved, but IO devices may crash or experience errors when attempting to access migrated pages
Solution Approach 1:
The system performs preliminary actions by setting migration state information in page table entries before actual page migration occurs. This allows the system to prepare for migration by marking pages as migratable while maintaining current access patterns, thus preventing IO device crashes during migration.
Solution Approach 2:
The migration state information in page table entries acts as an intermediary mechanism between the automatic migration system and IO devices. It provides a communication channel that allows the migration system to signal migration intentions to IO devices without requiring direct interaction, thus maintaining both automation and reliability.
2Productivity
If pages of memory are migrated to optimize storage location, then memory access efficiency is improved, but IO devices without migration support cannot handle the migration and may crash
Solution Approach 1:
The system segments the memory management functionality by separating the migration control logic into page table entry metadata. This allows legacy IO devices to continue operating without migration support while the system maintains migration capabilities for other components, thus improving adaptability without sacrificing productivity.
Solution Approach 2:
The page table entry structure is enhanced with migration state information that serves multiple functions: it enables migration for modern components while maintaining compatibility with legacy IO devices. This universal approach allows the same memory management system to serve both migrated and non-migrated access patterns.
3Reliability
If migration state information is added to page table entries to control IO device access, then migration reliability is improved, but device complexity increases
Solution Approach 1:
The migration state information is merged into the existing page table entry structure as metadata rather than requiring separate data structures. This combines multiple functions (address translation, access control, and migration management) into a single unified structure, improving reliability without proportionally increasing complexity.
Data Source
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AI summary
An electronic device includes a memory, an input-output memory management unit (IOMMU), a processor that executes a software entity, and a page migration engine. The software entity and the page migration engine perform operations for preparing to migrate a page of memory that is accessible by the at least one IO device in the memory, the software entity and the page migration engine set migration state information in a page table entry for the page of memory based on the operations being performed. When the operations for preparing to migrate the page of memory are completed, the page migration engine migrates the page of memory in the memory. The IOMMU uses the migration state information in the page table entry to control one or more operations of the IOMMU.