> Note that the size of VM stack is number of Objects and memsize of stack is vm_stacksize * sizeof(VALUE) bytes.
> Also note that this patch enable to change only VM stack size, but not machine stack size. I think when Fiber is implemented based on makecontext/swapcontext (FIBER_USE_NATIVE=1), machine stack size (default: 64KB) can beonfigurable. I wonder if procedures like `parse_some_big_xml' in Mike's example also need larger machine stack size? Does anyone have such a testcase?

Eek!
I don't think we should export vm_stack. It's purely implementation
detail. Just expose "stack size"
knob and it should change both vm-stack and machine-stack size.

btw, 64KB is bad default value. It's too strongly optimized 32bit
environment. It should have
larger value at least if 64bit.