On Sun, Mar 30, 2008 at 01:04:09PM +0300, Lars Nood??n wrote:
> Douglas A. Tutty wrote:
> > ... Shrinking the kernel would be the only reason I would
> > have of touching the kernel as I'm not into trying out
> > experimental features. It would be too bad if config doesn't
> > do this...
>
> Nick Holland wrote:
> > config strictly deactivates the drivers, it doesn't reduce memory
> > consumption or disk footprint.
> > ...
>
> Digressing slightly into config and what's in the FAQ regarding why or
> why not to deviate from GENERIC...
>
> Using config to modify the GENERIC kernel's settings can apparently
> improve boot speed. So maybe config should be mentioned in section 5.6
> of the FAQ, "Why do I need a custom kernel?" to steer those wondering
> about improving boot time away from trying unnecessarily to create a
> custom kernel.
>
> e.g. for B' 5.6, "Why do I need a custom kernel?"
>
> Removing device drivers may speed the boot process on
> your system, but can complicate recovery should you have
> a hardware problem, and is very often done wrong. config
> can be used instead of re-compiling to modify kernel parameters
> and speed booting. See the section of the config(8) man page
> on "kernel modification"
>
> > Since OpenBSD uses a monolithic kernel, it is outside the ability of
> > config to physically remove the deactivated drivers. ...
>
> That could also be useful to have in the FAQ somewhere. It's explicit
> in the kernel's nature, but could be mentioned for those who miss the
> ramifications of using a monolithic kernel.
>
> > Removing drivers for reduced memory is really a "for advanced users
> > only" task, and you VERY QUICKLY run into diminishing returns.
>
> That can be emphasized more heavily by moving forward one sentence in
> section 5.6, and adding that in.
>
> e.g. for the very start of B' 5.6:
>
> "Actually, you probably don't. Only the most advanced and
> knowledgeable users with the most demanding applications
> need to worry about a customized kernel or system, and even
> then you very quickly run into diminishing returns."
I know that on a regular i386 machine, its far easier to add a bit of
ram than to fitz with the kernel. I had seen on this list a while ago
someone needing to fitz with the kernel for putting OBSD on some
imbedded device. He (she?) wasn't building on the imbedded device, just
wanted to pare down memory usage as much as possible.
So perhaps to add to this entry for the FAQ, something that address this
desire to shrink the kernel to save memory:
"... For standard i386 old computers with little ram,
recompiling the kernel does not provide enough free memory to
affect what you can then do with that old computer. You are far
better to just add a bit more ram."
I know that other distros have dropped actual 386 CPUs from their
supported list so that i386 actually needs minimum 486. The reasoning
I've heard is that the amount of memory required is too much for any
remaining actual 386 boxes to actually have.
I know that my old PS/2 Model 70-A21 was a 386 with 4 MB Ram (at $1K per
MB) and I think it could take a maximum 16 MB (but my memory from 1988
is very fuzzy). Where there any 386 boxes that could take 32MB ram, and
do any still exist?
Doug.
