Re: if (CONFIG_FOO) Re: 2.4.0-test8-pre1 is quite bad / how about integrating Rik's VM

From: Alexander Viro (
Date: Wed Sep 06 2000 - 10:43:06 EST

On Wed, 6 Sep 2000, Martin MaD Douda wrote:

> Problem: every bloody line will go through the parser. There is too many
> lines. Compilation is realy slow today. I'm affraid this approach would
> make it worse. Note that 2.4.0-test7 has more than 2.75 milion lines.
> Or did you mean drivers will be (optionally?) excluded from this
> compile-it-all-and-then-optimize-it-away?

Do you always compile all *.c files? Notice that it doesn't equate to ifdefs
- e.g. if you have CONFIG_EXT2 undefined ext2 will not be compiled at all,
but there is no instance of CONFIG_EXT2 anywhere in *.[ch].

As for reducing compile time, try to feed the current tree through cpp and see
how much is included (and ignored) by preprocessor. I mean, just check how
much do we actually include and how little do we really need...

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