This question relates to a project that studies how to optimize
the memory of Java Virtual Machine.

Assume we have started a JVM process with a certain amount of
physical memory x. At runtime, we want to change the allocated
physical memory for JVM to y (y>x or y<x). Is this possible? Does
there exist a unix/linux/windows OS call to allow us to do this? Can we do
this for any process i.e. a non-JVM process?

Thank you very much.