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Date:      Sun, 19 Feb 2012 08:13:48 -0800
From:      perryh@pluto.rain.com
To:        dougb@freebsd.org
Cc:        sendtomatt@gmail.com, rank1seeker@gmail.com, hackers@freebsd.org
Subject:   Re: 8 to 9: Kernel modularization -- did it change?
Message-ID:  <4f411fbc.5xpQwqtOGVzi8G4D%perryh@pluto.rain.com>
In-Reply-To: <4F403C5E.4000104@FreeBSD.org>
References:  <CAOjFWZ6WM1bLEwaBiUE50Gj4MrwxefDWFb85ecRtYkSDuZ0erg@mail.gmail.com> <mailpost.1329495670.7246668.67851.mailing.freebsd.hackers@FreeBSD.cs.nctu.edu.tw> <4F3E8225.9030501@FreeBSD.org> <E1RyRKJ-000Ioa-Ec@hans3> <4F3E8C26.3080900@FreeBSD.org> <E1RyRq0-000Iqy-3l@hans3> <4F3EA5F2.9070804@gmail.com> <E1RyTZo-000J0R-0Y@hans3> <4F3EAE5F.6070903@gmail.com> <E1RyUv6-000J5e-0E@hans3> <20120217.220802.988.2@DOMY-PC> <4F3EDEBC.7040703@gmail.com> <4F3EFB70.5000102@FreeBSD.org> <4f3ff151.FznGzC6RC0a5qBKx%perryh@pluto.rain.com> <4F403C5E.4000104@FreeBSD.org>

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Doug Barton <dougb@freebsd.org> wrote:
> On 02/18/2012 10:43, perryh@pluto.rain.com wrote:
> > Doug Barton <dougb@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.



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