Re: [GIT pull] perf/urgent for 5.7-rc2

[Linus Torvalds]

On Mon, Apr 20, 2020 at 12:48 AM Ingo Molnar <mingo@xxxxxxxxxx> wrote:
>
> Fortunately, much of what objtool does against vmlinux.o can be
> parallelized in a rather straightforward fashion I believe, if we build
> with -ffunction-sections.

Well, I was actually thinking about a simpler model.

By "link time" I didn't mean "after final link". Yes, there may be
reasons to do it at that point too (to do any whole-program checks),
but that wasn't what I meant.

I meant literally doing it in the $(LD) and $(AR) phases, when you
still have lots of independent object files that you are just about to
link (or archive - do we even do that any more?) into one.

Then you'd parallelize exactly the same way we do now: one object file
at a time, and with no real change of semantics.

IOW, what I was thinking that instead of doing it as part of a final
step after the CC/AS, we'd do it as a preparatory step before the
LD/AR. Same exact operation, same exact target *.o files, just shifted
in time.

             Linus