Java webstart max-heap-size causes JVM cannot be started

Question

We use java webstart on the client side for a java swing based aplication. Recently we have been experiencing a weird "Cannot start java Virtual machine " error when clicking in the jnlp link.

We soon find out its because the max-heap-size setting in the jnlp file was set to 1024m whereas most of the clients PC only have 1 gb physical memory. Set the max-heap-size back to 512m solved the problem. Currently, the relevant line in the jnlp file looks like

 <j2se version="1.5+" initial-heap-size="100m" max-heap-size="512m"/>

I looked into the jnlp spec, but cannot find anything related to the "Java Virtual machine" issue. In theory the max-heap-size should not matter as much as the initial-heap-size. But our experience suggested quite the contrary.

The client environment:

Windows XP SP2 ( 32bit ), Internet Explorer 8.06, Memory 1G Note max-heap-size set to 1024m can cause the same problem on a machine with 2G ram.

Basically, what I am looking for here is some reference/spec/experience about why this is happening, and if there is any get-round for this issue besides increasing the physical memory size.

Another thing is that if we leave the max-heap-size unspecified, will the actual physical memory size be used as the max-heap-size, or a system-default one will be used?

Thanks, JasonW

Answer 1

It is likely that this problem is caused by the fact that a sufficiently large memory area could not be allocated to your JVM. The Java object heap has to be allocated in contiguous virtual addresses, for implementation reasons.

I noticed that on a Win XP box with 2 Gb RAM this breaks at around 1.5 GB (this off course varies depending on what processes are running on each PC, so YMMV).

Checkout the following posts for some explanations:

Java maximum memory on Windows XP

Why is the maximum size of the Java heap fixed?