vm size (task manager) vs. heap size java application

Question

I want to find a memory leak in a Java 1.5 application. I use JProfiler for profiling. I see using the windows' task manager that the vm size for my application is about 790000KB (increased from approx 300000KB). In the profiler I see that that the allocated heap is 266MB (increasing also). Probably it's a rookie question but, what else can occupy so much memory besides the heap so that it goes to approx 700MB vm size (or private bytes size)? I mention that there are approx 1200 threads running, which can occupy, according to an answer from here quite some memory, but I think there still is some space until 700MB. By the way, how I can see how much memory the threads stacks occupy? Thanks. JavaScript questions and answers, JavaScript questions pdf, JavaScript question bank, JavaScript questions and answers pdf, mcq on JavaScript pdf, JavaScript questions and solutions, JavaScript mcq Test , Interview JavaScript questions, JavaScript Questions for Interview, JavaScript MCQ (Multiple Choice Questions)

Answer 1

The JVM can use alot of virtual memory which may not use resident memory. On startup it allocates the heap, and maps in its shared libraries. Classes which are loaded use Perm Gen space. An application can use direct memory which can be as large as the heap maximum. As each thread is created a stack is allocated for each thread. In each case until this memory is used, it might not be allocated to the application i.e. not use physical memory. As the application warms up, more of the virtual memory can become physical memory. If you believe your JVM is not running efficiently, the first thing I would try is Java 6 which has had many fixes and improvements since the last release of Java 5.0.