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

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Message-ID: <CA+icZUVEkA6+5d3NGy7_G8eiaPvJkO_JCAX=XQwT1qpiGkLMWw@mail.gmail.com>
Date:   Sat, 13 Mar 2021 13:10:29 +0100
From:   Sedat Dilek <sedat.dilek@...il.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
        rostedt@...dmis.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 Sat, Mar 13, 2021 at 9:51 AM Borislav Petkov <bp@...en8.de> wrote:
>
> On Sat, Mar 13, 2021 at 06:26:15AM +0100, Sedat Dilek wrote:
> > x86/jump_label: Mark arguments as const to satisfy asm constraints
>
> Where do I find this patch?
>

Here we go:

https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/patch/?id=864b435514b286c0be2a38a02f487aa28d990ef8

> > x86: Remove dynamic NOP selection
> > objtool,x86: Use asm/nops.h
> >
> > My benchmark was to build a Linux-kernel with LLVM/Clang v12.0.0-rc3
> > on Debian/testing AMD64.
> >
> > Patchset applied for a first build:
> >
> >  Performance counter stats for 'make V=1 -j4 LLVM=1 LLVM_IAS=1
> > PAHOLE=/opt/pahole/bin/pahole LOCALVERSION=-7-amd64-clang12-cfi
> > KBUILD_VERBOSE=1 KBUILD_BUILD_HOST=iniza
>
> There's a reason I have -s for silent in the build - printing output
> during the build creates a *lot* of variance. And you have excessive
> printing with V=1 and KBUILD_VERBOSE=1.
>
> Also, you need to repeat those workloads a couple of times - one is not
> enough. That's why I have --repeat 5 in there.
>
> Also, you need --pre=/root/bin/pre-build-kernel.sh where that script is:
>
> ---
> #!/bin/bash
> echo $0
>
> make -s clean
> echo 3 > /proc/sys/vm/drop_caches
> ---
>
> so that you can avoid pagecache influence.
>

OK, I see.

- Sedat -

> Lemme rerun here with clang.
>
> --
> Regards/Gruss,
>     Boris.
>
> https://people.kernel.org/tglx/notes-about-netiquette