Java Virtual Machine Memory Management Strategy

Virtual machine, which stands against with our ordinary realistic computer, is just a concept. It's an imagining software system, which can be used to simulate the real computer. The advantage of virtual machine is it can reuse the programs on the different operating system, say the portability of application program. The design mechanism of Java Virtual Machine reflects this character very well.This paper takes the memory management in Java virtual machine as the research field, deeply analysis and research the key technique in it. Based on the traditional generation garbage collection, the author supplies a new memory management method, which is suitable for the embedded system. The work on this paper can be described as follows:First, the new method improved the object's layout in the memory, put the data and reference in different domain, and use the 4 bytes alignment to which ease the garbage collector to find the object reference domain. Second, the new method uses the mark-and-sweep mechanism to clean up the garbage memory in the old generation, and utilizes the copy mechanism for new generation. The dynamic generation-division was imported into the new method. During the long-life objects'promotion, it use the dest block as buffer, to facilitate and speed up the promotion progress. In the new generation, the dynamic size-adjust method was used, to reduce the influence caused by the garbage collector.At last, the author gives a simple example, to show the disadvantage of this new method, and points out how to avoid it.