Demand Paging Window for Embedded Memory Management
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Solution Overview
Problem
Demand paging is not supported in most embedded systems due to their complex mechanisms, making it difficult to implement, especially in systems without an operating system supporting virtual address spaces, which hinders efficient memory usage and real-time responses.
Innovation Solution
A demand paging apparatus and method for embedded systems that includes a nonvolatile storage device, physical memory processing, a demand paging window, and a demand paging manager, which generates page faults and processes them independently of the operating system, allowing demand paging to occur within an address space controlled by an application program.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If demand paging is implemented using a conventional operating system-level mechanism, then memory management efficiency is improved, but system complexity increases and real-time response becomes unpredictable
Solution Approach 1:
The patent extracts the demand paging function from the operating system level and implements it at the application level through a demand paging window. This allows the core memory management efficiency benefits of demand paging to be retained while avoiding the complexity of OS-level implementation, as the mechanism is now independent of the operating system and can be applied to systems without traditional OS support for virtual address spaces.
Solution Approach 2:
The patent segments the address space into a demand paging window and other regions, allowing demand paging to be applied selectively to specific memory regions rather than requiring system-wide implementation. This segmentation enables real-time critical sections to be excluded from demand paging while allowing non-critical sections to benefit from memory efficiency, thus maintaining predictable real-time response.
2Quantity of substance
If demand paging is applied to handle increasing code and data sizes, then memory capacity is improved, but real-time response predictability deteriorates
Solution Approach 1:
The patent applies different memory management qualities to different regions of the address space by creating a demand paging window that selectively applies demand paging only to non-real-time critical sections. This allows the system to handle larger code and data sizes in the demand paging region while maintaining predictable real-time response in regions excluded from demand paging, thus resolving the contradiction between memory capacity and real-time response predictability.
3Adaptability or versatility
If an operating system supporting demand paging is used, then virtual memory management is improved, but system adaptability to different embedded systems deteriorates
Solution Approach 1:
The patent creates a universal demand paging mechanism that can be implemented across different embedded systems regardless of whether they use an operating system or not. By implementing demand paging at the application level through a demand paging window rather than requiring OS-level support, the solution becomes adaptable to various embedded system configurations, from those with full OS support to those with no OS, thus achieving universality.
Data Source
AI summary
A demand paging apparatus and a method for an embedded system are provided. The demand paging apparatus includes a nonvolatile storage device, a physical memory, a demand paging window, and a demand paging manager. The nonvolatile storage device stores code and data which are handled by demand paging. The physical memory processes information about a requested page that is read from the nonvolatile storage device. The demand paging window generates a fault for the page and, thus, causes demand paging to occur. The demand paging window is part of an address space to which an application program stored in the nonvolatile storage device refers. The demand paging manager processes the page fault generated in the demand paging window.