Nonintrusive Page Table Switching During Logical Partition Migration
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Solution Overview
Problem
Data migration in logically partitioned environments often results in software installation problems, data loss, or corruption, leading to costly system errors and downtime, due to the complexity of maintaining the state of migrating partitions and the potential for manual tracking of memory updates being slow and tedious.
Innovation Solution
An apparatus and method that enable nonintrusive switching of page tables during migration by using a first page table to store initial page entries and a second page table to store entries generated during migration, with concurrent invalidation and updating of entries to maintain data integrity and minimize downtime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual tracking of memory updates is used during migration, then data integrity can be maintained, but the process becomes slow and tedious causing system downtime
Solution Approach 1:
The patent introduces a second page table as an intermediary structure during migration. This second page table captures memory updates generated during migration without requiring manual tracking, thereby maintaining data integrity while automating the process and improving migration speed
Solution Approach 2:
The patent creates a copy of the page table structure (second page table) to track memory updates during migration. This copying mechanism allows automatic recording of updates without manual intervention, resolving the contradiction between maintaining integrity and improving speed
2Device complexity
If a single page table is used during migration, then device complexity is reduced, but data integrity cannot be maintained due to concurrent updates
Solution Approach 1:
The patent segments the page table functionality into two separate page tables: a first page table for the source logical partition and a second page table for tracking updates during migration. This segmentation allows concurrent operations without compromising data integrity
Solution Approach 2:
The second page table serves as an intermediary that captures memory updates during migration. By routing update tracking through this intermediate structure, the system maintains integrity while managing the complexity of concurrent updates
3Productivity
If migration is performed with interrupt handling, then operational continuity is maintained, but the complexity of tracking memory updates increases
Solution Approach 1:
The second page table automatically captures memory updates generated during migration without requiring external tracking mechanisms. This self-service approach maintains operational continuity while reducing the complexity of update tracking
Data Source
AI summary
Maintaining data integrity for a logical partition by enabling nonintrusive switching of page tables used during a migration of the logical partition from a source computer system to a target computer system. A first page table stores a plurality of page entries made within a logically partitioned environment. A second page table stores one or more page entries generated during the migration. After migration, the processor page table pointer is switched to point to the first page table. A page entry in the second page table corresponding to a page entry made to the first page table by the logical partition may be invalidated in response to a page table hypervisor call made by the logical partition. In parallel, a plurality of entries generated during the migration of the logical partition in the second page table may be read through and invalidated.