I read in another question that you can increase the JRE memory allowance for an app through Window -> Preferences in Eclipse, but I can’t seem to find anything related to heap memory allocation. Editing -xms/xmx values in eclipse.ini doesn’t help since those are for Eclipse itself.
I believe when Run > Debug Configuration (or Run Configuration), then Arguments tab and in the VM arguments input you can specify arguments you want to use there.
NOTE: Eclipse has this to say about
VM Arguments: Values meant to change the behavior of the Java virtual machine (VM). For example, you may need to tell the VM whether to use a just-in-time (JIT) compiler, or you may need to specify the maximum heap size the VM should use. Refer to your VM’s documentation for more information about the available VM arguments.