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Date:      Wed, 24 Jan 2001 12:47:46 +1030
From:      Greg Lehey <grog@lemis.com>
To:        David Johnson <djohnson@acuson.com>
Cc:        Benjamin Lutz <benlutz@datacomm.ch>, freebsd-newbies@freebsd.org
Subject:   Re: Why is the FreeBSD kernel so much bigger than the Linux kernel?
Message-ID:  <20010124124746.L37060@wantadilla.lemis.com>
In-Reply-To: <3A6E3583.B5F42F16@acuson.com>; from djohnson@acuson.com on Tue, Jan 23, 2001 at 05:53:07PM -0800
References:  <NDBBKGBBKDPDNFIFCJEJEEDOCHAA.benlutz@datacomm.ch> <20010124115812.G37060@wantadilla.lemis.com> <3A6E3583.B5F42F16@acuson.com>

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On Tuesday, 23 January 2001 at 17:53:07 -0800, David Johnson wrote:
> Greg Lehey wrote:
>
>> I have a Linux box here:
>>
>> [grog@capellorosso /boot]$ ls -l /boot/vmlinux-2.2.16-22
>> -rwxr-xr-x    1 root     root      1621492 Aug 23 06:26 /boot/vmlinux-2.2.16-22
>>
>> That's not very different.  Note that a lot of hardware support in
>> Linux is done in loadable modules, while FreeBSD has it in the kernel.
>
> Your Linux is a default kernel off of some distribution (the -22 gives
> it away). A 2.2.16 kernel I just compiled to support only the hardware
> actually present on the system weighs in at only 416,492 bytes. That's a
> quarter the size you gave. (a FreeBSD kernel compiled for the same
> system was over one megabyte).

It's also compressed.

> Granted, FreeBSD has a different architecture than Linux. Comparing
> the sizes of the kernels is like comparing apples and oranges. But
> Ben's question was a good one, so I'll expand on it. Does putting
> the hardware support into the kernel instead of modules account for
> this big of a difference?

I don't know.  As  you say, the comparison isn't too meaningful
anyway.  I suspect that new things like the CAM layer are much bigger
than their old counterparts.  My first BSD/386 kernel was only about
600 kB, so there has been a lot of growth.

Greg
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