This question is asked in our internal discussion list. One of the kernel developer answered the question below:
LoadLibrary(AlreadyLoadedModule) has to increment the reference count of AlreadyLoadedModule, plus all of that module's dependencies, and their dependencies, recursively. Since the dependencies are recorded by name, not by a pointer to the loader entry, finding each dependency requires applying the isolation/redirection info in the activation context. For a module with a lot of imports, or imports which have their own large trees, this makes a LoadLibrary call quite expensive, even if it's already loaded.
GetModuleHandle is a better alternative.
This is a FYI post. I won't answer any question.