Microkernel: The Comeback?

bariswheel writes "In a paper co-authored by the Microkernel Maestro Andrew Tanenbaum, the fragility of modern kernels are addressed: "Current operating systems have two characteristics that make them unreliable and insecure: They are huge and they have very poor fault isolation. The Linux kernel has more than 2.5 million lines of code; the Windows XP kernel is more than twice as large." Consider this analogy: "Modern ships have multiple compartments within the hull; if one compartment springs a leak, only that one is flooded, not the entire hull. Current operating systems are like ships before compartmentalization was invented: Every leak can sink the ship." Clearly one argument here is security and reliability has surpassed performance in terms of priorities. Let's see if our good friend Linus chimes in here; hopefully we'll have ourselves another friendly conversation."

Comments

A false dichotomy

[The Conductor]

I seem to find this microkernel vs. monolithic argument a bit a of a false dichotomy. Micorkernels are just at one end of a modularity vs. $other_goal trade-off. There are a thousand steps in-between. So we see implementations (like the Amiga for example) that are almost microkernels, at which the purists shout objections (the Amiga permits interrupt handlers that bypass the OS-supplied services, for example). We also see utter kludges (Windows for example) improve their modularity as backwards compatibility and monopolizing marketing tactics permit (not much, but you have to say things have improved since Win3.1).

When viewed as a Platonic Ideal, a microkernel architechture is a useful way to think about an OS, but most real-world applications will have to make compromises for compatibility, performance, quirky hardware, schedule, marketing glitz, and so on. That's just the way it is.

In other words, I'd rather have a microkernel than a monolithic kernel, but I would rather have a monolithic kernel that does what I need (runs my software, runs on my hardware, runs fast) that a micokernel that sits in a lab. It is more realistic to ask for a kernel that is more microkernel-like, but still does what I need.

OS X - First make it work, then make it fast

[alispguru]

How many times have we all heard that the proper way to develop software is:

First make it work, then make it fast

Specifically:

Write it as simply and cleanly as you can,

THEN check performance,

THEN optimize, but ONLY where measurement tells you to.

Judging by the performance improvements over time, this is what the OS X team has been doing. Their stuff has been getting bigger, with more functionality, AND faster on the same hardware, with each release. If anyone else has been doing that, I haven't heard of it.

Virtualization

[jefu]

I suspect that virtualization may well signal the rise of the microkernel (exokernel?) again.

It seems reasonable to think that a tiny microkernel built for virtualization and able to support multiple virtual os's with minimal overhead is really going to be a very attractive platform. If we then get minimal, very application specific kernels to run on top of it for specific needs, we could get an environment in which various applications (http servers, databases, network servers of other sorts, browsers) could run in secure environments which could leverage multi-processor architectures, provide for increased user security, make inter-os communications work nicely and generally be a Good Thing. Certainly that would not prohibit running complete unix/MS/??? systems from running as well. (Granting, of course, that OS vendors go along with the idea, which some of the big players may find economically threatening.)

Could be very fun stuff and make viable setups that are currently difficult or impossible to manage well.