8 to 9: Kernel modularization -- did it change?

[perryh at pluto.rain.com]

Doug Barton <dougb at freebsd.org> wrote:
> On 02/18/2012 10:43, perryh at pluto.rain.com wrote:
> > Doug Barton <dougb at freebsd.org> wrote:
> >> loading modules through loader.conf is
> >> veeeeeerrrrryyyyyy sssssllllloooooowwwwww ...
> > 
> > Is it noticeably slower to load (say) a 6MB kernel + 2MB of
> > modules than to load an 8MB kernel?  
>
> I don't know, that wasn't the problem I was trying to solve.

Given the context of the thread, this:

> >> loading modules through loader.conf is
> >> veeeeeerrrrryyyyyy sssssllllloooooowwwwww ...

seemed to be an objection to modularizing the kernel.  Hence my
question:  is it in fact noticeably slower to load a minimal kernel
plus needed modules than to load a kernel that had all those modules
built in?  Based on the below, I think we agree that the answer is
likely to be no, even if all the modules in question were loaded
via loader.conf (and the modular version might well load noticeably
_faster_ if a sizeable fraction of the modules could be loaded via
kld_list instead).

> If your question is, "6 + 2-in-loader-conf" then I imagine that
> it would be about the same speed, maybe a little slower due to
> extra file open-read-close cycles. If it's "6 + 2-in-kld_list"
> then I imagine it would be quite a bit faster than an 8 M kernel
> ...

That is what I would expect, also.

> but I look forward to the results of your testing. :)

You're asking me to test _your_ assertion?  I had expected that
you would already have the data to back it up.