[RFC] subsystems vs. modules

Hi there,

until now, I had a tendency to split a library into several systems (more or less without thinking much) as soon as such or such feature was conditional (e.g. depending on CFFI availability, thread support, etc.).

Now I realize that in many cases, a conditionally included module or component would suffice, and so I'm starting to think that maybe I should do that, unless it makes sense for the conditional part to be loaded sort of standalone, independently from the rest, in which case a subsystem is more appropriate.

So my question is: WDYT, is there a general recommendation about this?

Thanks.