Embedded Java Virtual Machine Memory Management Technology Research

With the development of embedded technology, especially in the 3Gcommunication terminal, more and more people demand for the multimediaapplication that can be downloaded dynamically with abundant content. EmbeddedJava technology appears with it. But JVM is the key of succeeding in porting Javatechnology to embedded system. How to excavate the greatest latent energy of JVMin small devices with limited resource, there are a lot of respects deserved discussion.JVM is a kind of software. As to Java program, it is shown as the computer ofsoftware with single hardware and operating system characteristic. It makes Javaprogram possess the high portability among different computer systems. It is veryimportant that there is a steady and customized JVM in embedded system, so thesmall, resource-constrained embedded devices need an optimized JVM for embeddedsystem enviroments specially.In C/C ++ language, programmer must finish the allocation and collection ofmemory by himself. But Java environment has adopted the automatic memory toallocate and collect. After producing a class instance, JVM allocates automaticlymemory for it, and calls garbage collector to collect useless memory. This makesprogrammer needn't return memory to system, and reduces possibility of memoryerrors in programs. But in the embedded devices, the greatest limitation of Java lies inlacking the historical information of memory and unable to guarantee responsabilityin real time. For this reason, according to the characteristic of embedded system, andin order to remedy the deficiency in the similar design at present we put forward anew-type memory management policy of JVM. It designs and accomplishes theobject space management in fast allocation and fast garbage collection, strengthensthe real-time running of system, and reduces the system phenomenon of stoppinggreatly.This thesis introduces the background, source and international and domesticsituations of the subject at first, and Java technology and embedded real-time systemare introduced briefly. Then the detailed introduction to the runtime data area is done.Through analysis of JVM memory management policy, especially research andanalysis of alloction and garbage collection algorithms, we put forward the policy ofJVM and apply in embedded JVM VTJVM. The test to VTJVM indicates this schemehas been improved a lot on performance. Summarize this system finally, and pointout the improvement in the future.