[GRLUG] Meeting agenda?

[Roberto Villarreal]

On Wednesday 11 October 2006 13:05, Michael Mol wrote:
> On 10/11/06, Roberto Villarreal <rvillarreal at mktec.com> wrote:
> > > 1) The only reason I can think of to be weary of modules is a
> > > bordering-on-paranoia fear of rootkits...  quite a few load as
> > > modules.  However, a few that I know of use only /dev/kmem or similar
> > > to bootstrap themselves into kernel-space - no module support needed.
> > > Otherwise, modules are functionally identical to compiled-in drivers.
> >
> > Another reason is because, like in my above scenario, if you *do* have to
> > compile your kernel, it will save you a whole lot of compile time!!!
>
> Not really.  The kernel build system does a decent job in keeping
> compile times light.  If you've compiled the kernel before, and you
> change a couple of options, the build system will compile only the
> parts that have changed.

Even that depends... for a fresh compile (assuming you get everything right 
the first, which for me is maybe 30% of the time), it is (on my machine) the 
difference between 9 minutes and 33 minutes.  And on your last comment, that 
is true, but you aren't assured that your kernel will be correct if you 
don't 'clean' between builds (I speak from experience here).  

My *guess* for this (and this is a guess, I haven't investigated) is that 
assuming that there is no magic other than what the 'make' system does, if 
you have a file named foo.c that has already been compiled, then as long as 
none of it's *file* dependencies have changed, it won't recompile.  But if 
foo.c has #IFDEFs for kernel options that have changed since the last build, 
if the actual files above it haven't changed because of the revised option, 
then foo.c won't be recompiled (which has 'new' code that becomes exposed as 
a result of the #IFDEF).  

Roberto