An Efficient Page Lock/Release OS Mechanism for Out-of-Core Embedded Applications

Embedded system applications are becoming more complex, requiring increased memory. However, additional physical memory increases system cost and power consumption. Virtual memory techniques such as paging, can make use of low-power auxiliary memory, allowing applications increased memory for execution. Currently paging yields poor performance due to page swapping overheads. This paper presents a combined approach of using application hints along with an efficient page lock/release mechanism in the OS to reduce paging overheads. This makes paging a viable solution to support out-of-core embedded real-time applications. The Co-operative Application Specific Paging (CASP) mechanism presented works in conjunction with most existing page replacement policies, providing explicit support for applications via insertion of paging hints in the application source code. Both automatic and manual methods of inserting hints are described and evaluated. The benchmark results of a CASP implementation in the Linux 2.6.16 kernel have shown significant reduction in the number of page-faults (22.3%) and a considerable improvement in application execution times (12.5%).