[ale] Monolithic vs Modularised Kernels

[Danny Cox]

Raju,

On Wed, 2003-07-09 at 08:56, Raju wrote:
> The Client that I am doing for is finally pushing Linux into the
> enterprise. Amazing how chap11 can actually help promote better and much
> more superior technologies ;-). I am feverishly replacing a lot of the
> servers with Linux (Redhat) that use to the run the piece of sh!%$^%$ NT ,
> but using a vanilla kernel with the grsecurity patch. Some examples are,
> Samba for the PDC, WINS, Print Server, and even the  production database
> running Sybase (HP-UX) will soon be on Linux. My question is whether to
> build a Monolithic or Modularised Kernel. Read several arguments on
> google, but wanted to see your views. Thanks.

	Personally, I always use a kernel I built myself.  It's smaller in at
least two ways:

	1) modules aren't free.  They typically take just a bit more RAM than
if it was built in.  This isn't just in the extra module linkage, but in
some trampoline code that is required to run a module's code.  Something
about the RAM the module's code lives in isn't part of the kernel's
address space, and so an extra indirection must be made to access any
kernel memory location.

	2) if you use a module that will be loaded all the time, then what's
the point of using a module?  Think of an ethernet driver, for example. 

	Totally modulear kernels are great for distributions like RedHat or
SuSE, because they work out of the box.  If you build your own, though,
it will have only those drivers and features you want to have, and will
typically be smaller.

	HTH!

-- 
kernel, n.: A part of an operating system that preserves the
medieval traditions of sorcery and black art.

Danny

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