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Comment by sliken | Hacker News Reader

The post seems to be confusing FreeBSD userspace (which OSX adopted parts of) and the FreeBSD kernel (which has the mentioned lower network latency). OSX didn't adopt the FreeBSD kernel, but instead started with the Mach microkernel and has been going in their own direction since.

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Not just userspace - OSX adopted large pieces of FreeBSD kernel, including the syscall layer and the network stack. Also, Mach isn't technically a microkernel - the whole kernel runs in Ring 0.

But yeah, OSX kernel is vastly different from FreeBSD - first, there were huge differences to start with, only some pieces of kernel were adopted, and finally there were thousands of man-hours put into each system afterwards, diverging them even more.

Not that it matters (the post is mostly just unfounded opinion), but:

> OSX didn't adopt the FreeBSD kernel, but instead started with the Mach microkernel and has been going in their own direction since.

MacOS kernel uses a combination of Mach and BSD kernel code. It started with 4.4BSD, and at some point the bulk of BSD code was updated with code from FreeBSD 5.

After that, it was piecewise updated with more modern stuff, the MAC framework (used to implement sandboxing on iOS and macOS) and DTrace from newer FreeBSD kernels.

There is a great talk on OS X internals from CCC here:

https://events.ccc.de/congress/2007/Fahrplan/attachments/105...

It particularly talks about the unique hybrid kernel approach and how there is nothing like it.

BSD itself took the VM subsystem from Mach (so BSD is kind of an interesting hybrid as well). While it has been heavily modified in the last 25+ years, the VM portion of the FreeBSD kernel is still stylistically distinct from BSD portions of the kernel source code.

A better explanation I think is found here:

https://lists.freebsd.org/pipermail/freebsd-advocacy/2008-Au...

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