Effective Compaction for Kernel Memory Allocator Using Workload Distribution

Abstract

Low latency is one of the most important requirements for smart devices. Even though they have a small amount of memory, end users often want to run multiple applications concurrently without delays. Memory fragmentation is a critical obstacle to this aspect. To recover from it, the operating system uses compaction to create contiguous space from scattered free pages. Memory compaction tends to secure as many contiguous memory pages as it can, which may affect the user experience adversely at application launches. In this paper, a new page compaction method is proposed to improve the user experience. This method employs an efficient mechanism to find candidate pages to move. It also uses a bitmap to represent the status of the physical pages and find compactable pages effectively. The experiment performed on the proposed method demonstrates that the interruptions for compaction occur more frequently, but with a significantly lower workload than conventional compaction. According to the experiment, the success rate after compaction increased by about 22%, and the elapsed time to scan free pages decreased dramatically compared to conventional compaction. Moreover, the proposed method reduced the worst-case time for a new process creation by about 67%.