Comment by sfink | Hacker News Reader

Comment by sfink | Hacker News Reader

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I'm kinda with rektide on this. It is true that eBPF is not itself a microkernel approach. But nobody is asserting that it is. The claim is that eBPF is a building block that allows emulating some microkernel characteristics on a monolithic kernel.

The final result is not what anyone would describe as a microkernel. But it does allow implementing things on top of a different API boundary. And microkernel vs monolithic kernel is all about where the API boundary lies. (And I don't mean the ring 0 boundary! If ring 0 is the only relevant definitional characteristic of "microkernel-ish" for you, then I agree to disagree.)

Said another way: if you consider driver-on-API-implemented-with-eBPF-on-monolithic-kernel, then looking from the bottom it will look nothing like a microkernel. Looking from the top, it will.

(rektide is not insisting that a golden retriever is actually a cat, they're saying that a golden retriever can keep the mice under control similar to how a cat might.)

But at this point, I doubt it really matters who agrees with what perspective!

As I said I have done research work and a written a PhD thesis on operating systems, and I've worked on several production kernels including Linux and I find it hard to fathom this hill you all are trying to die on. You can't just redefine important concepts however you like as the arguer is trying to do. Names mean things. If you want to pretend that x is y and blue is red, then we simply can't discuss the topic because you're not able to agree on the basic particles the community uses to have discussions. It's just contrarianism.

Microkernels are defined by privilege levels. It's not debatable. You wouldn't say that something is true microkernel because it's modular. We could have more interesting discussions about the actual topic if you and the original poster could accept common definitions like any sane technologist.

I agree that eBPF running on a monolithic kernel is not a microkernel. I agree that microkernels are defined by privilege levels. I would not say that something is true microkernel simply because it is modular. I would agree that I am not a fully sane technologist.

I disagree that it is impossible to emulate any characteristics of running on a microkernel when one is, in fact, running on a monolithic kernel.

Using one single narrow criteria to completely disregard any & all other similarity is a shame & a sham. This is a huge disservice & actively harmful to understanding the world.

I've said again and again microkernel-y microkernel-ish. But every single time I try to build a bridge & explain how it's similar but different, you burn it down. I think you have been poisoned by being too close to the subject matter & lack objective sensibility about the subject, are unable to adequately step back to actually understand. And you don't seem to have any interest in learning or trying to see, which is a crying shame.

I feel like you as a deep practioner/academic of this area should be best able to help explain relationships & similarities, to see connections. But you focus only on making distance & setting things apart. That's just not good enough. It's not sufficient a viewpoint.

> Using one single narrow criteria to completely disregard any & all other similarity is a shame & a sham. This is a huge disservice & actively harmful to understanding the world.

Just pick a different fucking word. Why do you want to use the term microkernel?

It’s like insisting that a rock is actually and airplane because they both fly through the air. It’s a pointless redefinition and everyone qualified to talk about things that fly won’t call it an airplane and will be confused about what you’re talking about.

It's not a redefinition when you add "-like" at the end. If I say a particular airplane flies like a rock, nobody needs to clarify that airplanes are not rocks.

But please refer back to the original comment. rektide said it was "un-monolithic", which it is. A virtual machine is less monolithic than baked-in code.

Softirq is the one who brought up microkernels specifically. Softirq is the one that repeatedly steered the conversation back to monokernel versus microkernel.

If you put words in someone's mouth repeatedly until they start using them, you lose the right to complain that they're using the wrong words!

"Why do you want to use the term microkernel?" is the exact opposite of what happened.

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