linux-kernel - Re: [GIT PULL] kprobes updates for v5.8

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Date:   Mon, 1 Jun 2020 12:56:07 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] kprobes updates for v5.8

On Mon, Jun 1, 2020 at 6:08 AM Ingo Molnar <mingo@...nel.org> wrote:
>
>  include/linux/compiler.h            | 53 +++++++++++++++++++++++

I have pulled this, but do we really want to add this to a header file
that is _so_ core that it gets included for basically every single
file built?

I don't even see those instrumentation_begin/end() things used
anywhere right now.

It seems excessive. That 53 lines is maybe not a lot, but it pushed
that header file to over 12kB, and while it's mostly comments, it's
extra IO and parsing basically for _every_ single file compiled in the
kernel.

For what appears to be absolutely zero upside right now, and I really
don't see why this should be in such a core header file!

I don't even see this as having anything at all to do with
"compiler.h" in the first place.

I really think we should think twice about making core header files
bigger like this. No, we're nowhere the disaster that C++ project
headers are, but tokenization and parsing is actually a pretty big
part of the build costs (which may surprise some people who think it's
all the fancy optimizations that cost a lot of CPU time).

                  Linus