Re: [PATCH v2 00/21] kbuild: significantly speed up kernel builds

[Kees Cook]

On Mon, Sep 14, 2026 at 07:25:28PM +0100, Lorenzo Stoakes (ARM) wrote:
> On Mon, Sep 14, 2026 at 08:41:39AM -0700, Kees Cook wrote:
> > Did you try Clang CONFIG_LTO=y builds?
> 
> I tried a CONFIG_LTO_CLANG_THIN in order to check that the *.mod.S stuff
> worked correctly, all working correctly.

Okay, thanks! I did the same just now too. It seems to be just fine.

> I can try to get some profiling numbers for thin and full if you want?

Mostly I wanted to know if it worked still, and I guess for profiling,
I'd want to make sure it didn't regress how long it took to build. :)

> Well I rewrote the majority of them, so this is a stinging critique of my
> commit message writing I guess :)

Oops! Sorry. I'll go through them again, but I felt like the objtool
commit logs were very long, but perhaps it is justified. ;)

> (N.B. I have had feedback like that on a fair few human-written commit
> messages of mine lately so there might be some validity to that ;)

And as I said, I get told I'm often too terse, so perhaps my sensing
here is broken. :P

> > One area I think might solved via an LLM is the 3-pass kallsyms stuff.
> > If we could get a deterministic kallsyms build in 1 pass, that would be
> > very nice. A lot of people have tried, but it has eluded upstreaming.
> 
> "going from three passes to one would save around 8s on an allmodconfig
> build and 2 to 3s on defconfig, out of tails that are currently roughly 25s
> and 8s." says the LLM :) so that actually does seem worthwhile.

It's what I'm always staring at when I do incrementals. ;)

> But I think best as a follow up?

Yeah, I would imagine it'd be separate. (I think a few of these sets of
changes could be landed separately too, like the pigz work.)

-- 
Kees Cook