Clock Synchronization via Offset Tables in Virtualized Systems
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Solution Overview
Problem
As the number of logical domains on an information processing apparatus increases, the frequency of access to the clock device also increases, leading to a higher load on the clock device and bus congestion, which reduces response speed, and poses challenges in maintaining time consistency across multiple clock devices.
Innovation Solution
Implementing a control unit that manages time-of-day differences between physical and logical domains, distributing clock access, and using a service processor to synchronize and maintain time across multiple clock devices, ensuring consistency without continuous correction of clock devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of logical domains implemented on an information processing apparatus is increased, then the processing capacity is improved, but the frequency of access to the clock device increases causing increased load and bus congestion
Solution Approach 1:
The patent divides the clock access management into segments by introducing a time-of-day offset table that stores individual offset values for each logical domain. This allows each logical domain to be independently managed with its own time offset, enabling parallel access to the clock device without requiring centralized coordination, thereby reducing the load on the clock device while maintaining processing capacity for multiple logical domains.
2Device complexity
If the number of clock devices provided in the information processing apparatus is increased, then the load on individual clock devices is reduced, but ensuring consistency in time of day becomes more difficult
Solution Approach 1:
The patent introduces a time-of-day offset table as an intermediary mechanism that mediates between multiple clock devices and logical domains. The offset table stores and manages time offset values for each logical domain, allowing the system to maintain time consistency across multiple clock devices without requiring them to be continuously synchronized with each other. This intermediary structure enables independent clock devices to serve multiple logical domains while maintaining reliability through centralized offset management.
3Measurement precision
If continuous correction of clock devices is performed to maintain time consistency, then time accuracy is improved, but processing overhead increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing time-of-day offsets for each logical domain in the offset table before actual time access occurs. When a logical domain needs to access the clock, the system simply retrieves the pre-stored offset value rather than performing continuous correction calculations. This preliminary preparation of offset values maintains time accuracy while significantly reducing the processing overhead during runtime operations.
Data Source
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AI summary
In an information processing apparatus, a control unit includes a first clock device for providing the time of day. A physical domain includes a second clock device, and implements a logical domain that functions as a virtual information processing apparatus. The control unit controls a first time-of-day difference between the time of day of the first clock device and that of the second clock device. The physical domain controls a second time-of-day difference between the time of day of the second clock device and that of the logical domain. In the information processing apparatus, the time of day on the logical domain is controlled based on the first and second time-of-day differences.