Re: Microkernel architecture?

[Gary Thorpe <gathorpe79@xxxxxxxxx>]

Yeah, an exokernel sounds cool...until you realize that every single 
application needs to be linked into libraries that implement an OS 
basically. What does that do for memory usage? How protected is the 
machine from malicious/errant applications? Security? IPC?

A microkernel makes it possible to modularize the OS, but an exokernel 
sounds like it forces all the applications to be monolithic OS+app 
hybrids. The speed comparisons on the ExOS web site don't even use a 
particularly fast web server for BSD (or is NCSA now considered high 
performance as well as obsolete?).

Pedro Giffuni wrote:

> This is off topic, (but just for reference and because there is not
> technical-chat list ...)
>
> when you mentioned you wanted a userland VFS API, I recalled someone already did
> that: in fact, they turned everything into libraries and made the kernel very
> small... they called it an Exokernel:
>
> http://www.pdos.lcs.mit.edu/exo.html
>
> They invented softupdates, BTW :).


I believe Sun funding some research into improving FFS and the resultant 
code first emerged on BSD:
http://www.netbsd.org/Documentation/tune/5.html#a3
http://www.netbsd.org/Documentation/misc/#softdeps
http://www.mckusick.com/softdep/index.html
http://www.usenix.org/publications/library/proceedings/usenix99/mckusick.html

No mention of exokernels...was it used for the development?

> cheers,
>
>     Pedro.