[halayli]

Vonn Neumann architecture is 80 yrs old. Why is it relevant how long a design is if it's still the most relevant and widely used one? The basic abstractions of unix v6 still holds to this day.

The main difference between Microkernels and Monolithic is how address space get to be shared between userland and kernel. I don't see how microkernel design would be "better". Why teach a design that isn't widely used?

[darby_nine]

The Vonn Neumann architecture does not expose the same structural flaws monolithic kernels do—namely, their (of course tendency in modern computing to be) massive size and their failure scenarios in the event of a problem.

Old is not always a problem, but monolithic kernels face the same problems they did in the 80s. It's not surprising Apple is moving away from kernel drivers and into userspace functionality.

[halayli]

My comment was in the context of which is better for learning purposes. You spun my comment and turned it into mono vs micro kernel.

System Design is about trade offs. You conveniently say "expose the same structural flaws monolithic kernels do" and not mention anything about microkernels. System arch discussions are not about who "wins", but about trade offs.

> but monolithic kernels face the same problems they did in the 80s

Putting your lack of balance aside, what problems are you talking about specifically? Are you aware of how many new instructions have been added since the 80s that were designed specifically to address the shortcomings of monolithic kernels? Microkernels, even when resources were much scarcer back in the 1980s, still did not become popular.

Both designs have their use cases. Micro and mono kernels have pros and cons but for learning purposes it makes more sense to teach about monolothic kernels since all popular operating systems follow this design.

[kragen]

apple started with mach, which was a microkernel, and linked basically all of the freebsd kernel into it, morphing it from a microkernel operating system into a monolithic operating system

i agree that monolithic kernels are unpleasant and brittle, but unfortunately they don't actually seem to be obsolete

[pjmlp]

NeXT you mean.

Additionally, Apple has a long term roadmap to fix that design decision, hence why they are killing one kernel subsystem at a time, moving them into userspace, with one year given for the developers to adopt each of them, after being made available as the new way.

Finally, it is kind of ironic that systems that have doubled down on monolithic kernels, are now used to run an endless pile of containers and Kubernetes clusters.

[darby_nine]

> hence why they are killing one kernel subsystem at a time, moving them into userspace, with one year given for the developers to adopt each of them, after being made available as the new way.

Notably they aren't exposing most of the functionality, it wouldn't be possible to e.g. implement NFS or 9p with the userspace filesystem thing they've been pushing. They're basically just shutting users out from their own computer....

[kragen]

well said

[darby_nine]

> apple started with mach, which was a microkernel, and linked basically all of the freebsd kernel into it, morphing it from a microkernel operating system into a monolithic operating system

The microkernel aspect of it had completely vanished by the time they hit the general public.

> i agree that monolithic kernels are unpleasant and brittle, but unfortunately they don't actually seem to be obsolete

Of course they aren't obsolete! The security in your phone depends directly on sel4, at least if you use an apple device. They just aren't relevant to most of the compute and most of the software you interact with today or in all of history.

[kragen]

you seem to have thought i said 'unfortunately microkernels aren't obsolete', but that is the opposite of what i said

[eschaton]

Mach as deployed at NeXT was also never a microkernel, and combined the BSD 4.2 kernel. I believe this is also effectively what OSF/1 did with the OSF variant of Mach.

Mach has basically always supported that kind of use, even back to early CMU research versions.

[userbinator]

It's not surprising Apple is moving away from kernel drivers and into userspace functionality.

That's largely a political decision because of Apple's totalitarianism.