linux-kernel - Re: [PATCH 0/2] x86: Remove ideal

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Date:   Fri, 12 Mar 2021 18:35:45 +0100
From:   Sedat Dilek <sedat.dilek@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
        hpa@...or.com, torvalds@...uxfoundation.org,
        linux-kernel@...r.kernel.org, linux-toolchains@...r.kernel.org,
        jpoimboe@...hat.com, alexei.starovoitov@...il.com,
        mhiramat@...nel.org
Subject: Re: [PATCH 0/2] x86: Remove ideal_nops[]

On Fri, Mar 12, 2021 at 6:26 PM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Fri, 12 Mar 2021 15:47:26 +0100
> Borislav Petkov <bp@...en8.de> wrote:
>
> > On Fri, Mar 12, 2021 at 03:29:48PM +0100, Sedat Dilek wrote:
> > > What does this change exactly mean to/for me?
> >
> > Probably nothing.
> >
> > I would be very surprised if it would be at all noticeable for you -
> > it's not like the kernel is executing long streams of NOPs in fast
> > paths.
> >
>
> With ftrace enabled, every function starts with a NOP. But that said, the
> simple answer is for Sedat to apply the patches on his box and do some
> performance testing. It doesn't matter if you are white, black, male,
> female, or anything in between. As my daughter's swim coach said; it's the
> numbers that matter here. Run a bunch of benchmarks on your box on the
> latest kernel, apply Peter's patches, and then run the benchmarks again on
> the latest kernel with Peter's patches and then report the difference. If
> it's negligible then there's nothing to worry about.
>

Hey Steve, you degraded me to a number :-).

I dunno which Git tree this patchset applies to, but I check if I can
apply the patchset to my current local Git.
Then build a kernel in the same build-environment.
Lemme see.

To say with Linus's words:
"Numbers talk - bullshit walks."

- Sedat -