Write-activity-aware page table management for PCM-based embedded systems

Due to its low power consumption and high density, phase change memory (PCM) becomes a promising main-memory alternative to DRAM in embedded systems. PCM, however, has the endurance problem in which the number of rewrites to each cell is quite limited compared with DRAM. Therefore, it is fundamental to eliminate unnecessary writes in PCM-based embedded systems. This paper presents a simple yet effective scheme to solve this problem, through redesigning existing software to exploit write-activity-aware features provided by underlying hardware. Particularly, we target at page table management, a key kernel component residing in the memory management part of the Linux kernel. We present for the first time a write-activity-aware page table management scheme, WAPTM, accomplished through two modifications to the page table initialization and page frame allocation process. The scheme has been implemented in Google Android 2.3 based on ARM architecture and evaluated with real applications on the Android emulator. The experimental results show that the proposed scheme can significantly reduce write activities to page tables in the new kernel compared with the original Android. We hope this work can serve as a first step towards the design of write-activity-aware operating systems via simple and feasible modifications.