On Dec 31 2007 16:19, Bodo Eggert wrote:
>Adrian Bunk wrote:
>>
>> The only advantage I see is that the kernel image you have to flash
>> can be made smaller - with the disadvantage that the running kernel
>> is bigger by more than 10%.
>>
>> If you don't believe me, try it yourself:
>> Build all drivers statically into your kernel, and then compare the
>> vmlinux sizes with CONFIG_MODULES=n and CONFIG_MODULES=y.
>
>If you'd aim for a small kernel image, you would build anything as a module
>that is not requred for booting.
>
Yes, there is a tradeoff for both.
Example:
16:30 ichi:../net/802 > l fc.o fc.ko
-rw-r--r-- 1 jengelh users 7961 Dec 27 15:19 fc.ko
-rw-r--r-- 1 jengelh users 2453 Dec 28 23:58 fc.o
(from a recent not-so-complete patch turning CONFIG_FC etc. into =m)
If fc was modular, it might save the 2453 bytes off the core kernel image,
but adds ~5508 bytes to disk.
So one has to pick =y or =m depending on whatever suits his/her situation.
But the choice should be _available_.
>>>> After all, changing it to a bool will allow us to make the
>>>> kernel image for nearly everyone smaller by a few hundred
>>>> bytes...
>>>
>>> I can't see why optionally building it as a module would force us
>>> to make the kernel bigger. It may be a little more ugly to
>>> support =m, but thats it, isn't it?
>>
>> On architectures like x86 where __exit code is freed at runtime
>> af_unix_exit() makes your kernel image (but not the running kernel)
>> bigger.
>>
>> With CONFIG_MODULES=y the 13 EXPORT_SYMBOL's that only exist for
>> the theoretical possibility of CONIG_UNIX=m waste a few hundred
>> bytes of memory.
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