What are the benefits of XNU using Mach features compared to a full FreeBSD kernel? [closed]

Solution 1:

I would argue that it is a bit too simplistic to say that the Darwin kernel is simply a hybrid of Mach and FreeBSD.

Trying to look at without the historic implications of why the architecture was chosen doesn't really make sense either. If you were to design a new operating system today, you wouldn't end up with the same result, as the choices available are vastly different now.

You have to remember that Darwin did not just "pop into existence" by merging source codes of Mach and FreeBSD. That is not at all the case. Instead Darwin descend from Rhapsody, which also a heavily customized mix of components such as OSFMK (Mach), 4.4BSD and Yellow Box (which would eventually become Cocoa).

If you have to look at the "objective benefits", you would find that there's probably few to none when looking at the choice between the current "hybrid-kernel" and a hypothetical monolithic Darwin kernel.

If you want to compare it to the actual FreeBSD kernel as of today, there's a huge amount of advantages - mostly related to the fact that Darwin can run Apple's existing code base.