Re: [PATCH 2/4] Core support for --combine -fwhole-program

David Woodhouse
2006-08-25T10:40:47Z

On Fri, 2006-08-25 at 12:30 +0200, Adrian Bunk wrote:
> My hope is "insane" would be something like "1 GB of RAM" that is no
> longer insane on current computers. [1]

Maybe -- but still, that's quite a steep requirement, and would also
require a fairly major redesign of the current kbuild architecture.

I'm inclined to stick with per-directory builds for now, which is both
relatively simple to implement and where the _majority_ of the benefit
it likely to be seen.

Whole-kernel optimisation is something I'm inclined to leave until LTO
happens -- but don't let me stop you from investigating it.

> > I suspected that most of the 'further savings' to which you refer above
> > could be achieved more easily with -ffunction-sections -fdata-sections
> > --gc-sections
>
> AFAIR -ffunction-sections/-fdata-sections cause some overhead in the
> resulting binary?

Not that I'm aware of. There's overhead in the resulting ELF files, but
we combine sections in the vmlinux.lds so there isn't even that overhead
in the vmlinux.

--
dwmw2