Re: [GIT] kbuild/lto changes for 3.15-rc1

Andi Kleen
2014-04-07T23:16:53Z

On Mon, Apr 07, 2014 at 10:19:19PM +0200, Michal Marek wrote:
> Hi Linus,
>
> besides the kbuild branch, here is the LTO build support by Andi. It is
> a separate branch, because it depends on other patches by Andi which
> were merged through other trees. The link-time-optimization build is an
> experimental feature, so there one kconfig option to enable it and
> another kconfig option to disable it (behind a door with a sign "Beware
> of the Leopard"...), so that it is not enabled by
> allmodconfig/allyesconfig.

Thanks Michal,

I should add this version builds quite a bit slower than other LTO trees,
because the single pass kallsyms didn't quite make it, so the Link
Time Optimization is re-done 2-3 times if KALLSYMS is enabled. That
will be hopefully fixed next cycle.

LTO will always be somewhat slower than a normal build, but right now
it's a lot slower because of this, depending on the size of the vmlinux.

-Andi