And THAT is the problem [LWN.net]

And THAT is the problem

Posted Aug 22, 2011 19:39 UTC (Mon) by HelloWorld (guest, #56129)
In reply to: And THAT is the problem by khim
Parent article: HP dropping webOS devices

> Ah, now we back to the whole BFS debate. No, I have no benchmarks present.
Well, then you don't really have a point, do you?

> Sure. It's typical problems for real programs.
Again, do you have any data to back this up? Because I really doubt that this is a problem for 99% of all applications.

> Because these are the same "wizards from Ivory Tower" that proclaimed 20 years ago "Among the people who actually design operating systems, the debate is essentially over. Microkernels have won."

> This was nice theory but practice is different. In practice two out of three surviving major OSes are microkernel-based only in name and one is not microkernel at all.
That doesn't mean anything as long as you don't show that the failure of microkernel based OSes on the desktop can be attributed directly to the microkernel design. There may well have been other factors: inertia, lack of hardware and software vendors, bad luck etc.. Also, microkernels were actually a success in the embedded world. QNX is just one example of this.

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And THAT is the problem

Posted Aug 23, 2011 5:00 UTC (Tue) by raven667 (subscriber, #5198) [Link]

Microkernels are also a success in the modern server world, the name has changed but the design is there, it is just called a hypervisor now

And THAT is the problem

Posted Aug 23, 2011 17:19 UTC (Tue) by bronson (subscriber, #4806) [Link]

I don't think this is true. Microkernels are a collection of OS processes interacting to provide a rich interface to userland (file systems, networking stack, IPC, etc), while hypervisors don't intend to provide OS services at all. They're just a thin hardware abstraction layer so that multiple operating systems (microkernel or not) can be fooled into coexisting and maybe some very coarse resource management.

Like atoms vs. the solar system, they might look similar if you look from afar. It's certainly possible to cherry-pick theoretical similarities. For real-world work, though, they tend to be quite different.

And THAT is the problem

Posted Aug 25, 2011 20:37 UTC (Thu) by raven667 (subscriber, #5198) [Link]

I was thinking that the combination of the hypervisor and the guest kernel in total formed the microkernel. Each guest has its own personality and file systems, network, ipc, etc. Information is passed back and forth through the hypervisor using interfaces that happen to look a lot like network cards and block devices, or use PV drivers which can do pure message passing. The big thing is that every bit runs in its own protected memory space which I thought was the big difference and value of a microkernel vs. a traditional kernel.

Like you said, I'm certainly standing from afar and squinting more than a little. 8-)