We present a comprehensive and quantitative study on the development of the Linux memory manager. The study examines 4587 committed patches over the last five years (2009-2015) since Linux version 2.6.32. Insights derived from this study concern the development process of the virtual memory system, including its patch distribution and patterns, and techniques for memory optimizations and semantics. Specifically, we find that the changes to memory manager are highly centralized around the key functionalities, such as memory allocator, page fault handler and memory resource controller. The well-developed memory manager still suffers from increasing number of bugs unexpectedly. And the memory optimizations mainly focus on data structures, memory policies and fast path. To the best of our knowledge, this is the first such study on the virtual memory system.