Re: Paging in Minix [LWN.net]

Re: Paging in Minix

Posted Feb 6, 2007 12:52 UTC (Tue) by dune73 (subscriber, #17225)
In reply to: Comparing Linux and Minix by iabervon
Parent article: Comparing Linux and Minix

Adding paging to minix is one of the typical exercises of computer science classes.

The whole point of minix as a studying OS is, that it is incomplete, but ready to take new features.

Otherwise i think comparing the performance of Linux and Minix is unfair. It's comparing pears and apples.

Dr. Tanenbaum insists that at modular kernel runs at 90% of the performance of a monolithic one.
He does not argue, that his modular studying kernel written by him during a couple of months in the 80ies (and overhauled and slightely improved in the meantime) compares to a highly tuned kernel aimed for professional usage; written by hundreds of developers investing possibly hundreds of man-years.

His point is: If you guys would invest the same amout of development-time into a modular kernel, it would perform at 90% while being a lot more stable.

Maybe he is right, maybe he is wrong. But until somebody tries it out, we won't know for sure.

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Minix's purpose is more than just an academic tool...

Posted Feb 6, 2007 14:58 UTC (Tue) by pr1268 (subscriber, #24648) [Link]

The features AST mention in Minix v.3 (on the Minix Web page) seem to indicate it's targeted not only for academia but also for some commercial usage (the page mentions "...cameras, DVD recorders, cell phones" and Minix's "BSD-type license").

That being said, I wonder if AST intentionally left some features out so that not only do students learn more about OS design by "finishing" Minix in the classroom, but also commercial users of Minix must also finish Minix to meet their custom needs, e.g. kind of like completing a partially-built system. Either that, or use Minix "as is" with just its existing features.

Granted, what I've read about AST indicates his primary motivation for writing Minix was/is for academic purposes - an endeavor he's pursued for the past several decades.

Re: Paging in Minix

Posted Feb 6, 2007 16:50 UTC (Tue) by musicon (subscriber, #4739) [Link]

Dr. Tanenbaum insists that at modular kernel runs at 90% of the performance of a monolithic one.

[...]

His point is: If you guys would invest the same amout of development-time into a modular kernel, it would perform at 90% while being a lot more stable.

Having not followed HURD especially closely, I wonder how it and Minix would compare performance-wise (and I'm sure there are differences between the Mach and L4 versions as well).

The last I read, there are several similar limitations such as partition size, application ports, and lack of tuning.

Re: Paging in Minix

Posted Feb 6, 2007 19:41 UTC (Tue) by oak (guest, #2786) [Link]

> Otherwise i think comparing the performance of Linux and Minix is
> unfair. It's comparing pears and apples.
>
> Dr. Tanenbaum insists that at modular kernel runs at 90% of the
> performance of a monolithic one.

Comparing feature slowdown with unoptimized kernels isn't necessarily
anything that would tell what kind of a slowdown the implementation
on a real system would have...

Lets say "=" is the time required to do an operation and "X" is slowdown
induced by a new feature:
=========X
Feature X has 10% slowdown, right?

Now do comparison with an optimized kernel:
=X
The slowdown of feature X is actually 100% for an optimized system...?

To get relevant numbers one should add the feature to a real system.
To be fair, final implementation of the feature could be much faster
than the initial prototype too... :-)