linux-kernel - AW: [PATCH] Makefile.debug: support for -gz=zstd

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Message-ID: <DU0PR03MB8319EF26082FA49D1F60DFCCF3319@DU0PR03MB8319.eurprd03.prod.outlook.com>
Date:   Tue, 25 Oct 2022 17:08:12 +0000
From:   "Sedat Dilek (DHL Supply Chain)" <sedat.dilek@....com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>,
        "sedat.dilek@...il.com" <sedat.dilek@...il.com>,
        Masahiro Yamada <masahiroy@...nel.org>
CC:     Nathan Chancellor <nathan@...nel.org>,
        Fangrui Song <maskray@...gle.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Terrell <terrelln@...com>, "Tom Rix" <trix@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        David Gow <davidgow@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        "Dan Williams" <dan.j.williams@...el.com>,
        Miguel Ojeda <ojeda@...nel.org>,
        Isabella Basso <isabbasso@...eup.net>,
        Vlastimil Babka <vbabka@...e.cz>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-kbuild@...r.kernel.org" <linux-kbuild@...r.kernel.org>,
        "llvm@...ts.linux.dev" <llvm@...ts.linux.dev>
Subject: AW: [PATCH] Makefile.debug: support for -gz=zstd



-----Ursprüngliche Nachricht-----
Von: Nick Desaulniers <ndesaulniers@...gle.com> 
Gesendet: Montag, 24. Oktober 2022 19:44
An: sedat.dilek@...il.com; Masahiro Yamada <masahiroy@...nel.org>
Cc: Nathan Chancellor <nathan@...nel.org>; Fangrui Song <maskray@...gle.com>; Sedat Dilek (DHL Supply Chain) <sedat.dilek@....com>; Michal Marek <michal.lkml@...kovi.net>; Nick Terrell <terrelln@...com>; Tom Rix <trix@...hat.com>; Andrew Morton <akpm@...ux-foundation.org>; Peter Zijlstra (Intel) <peterz@...radead.org>; David Gow <davidgow@...gle.com>; Kees Cook <keescook@...omium.org>; Josh Poimboeuf <jpoimboe@...nel.org>; Dan Williams <dan.j.williams@...el.com>; Miguel Ojeda <ojeda@...nel.org>; Isabella Basso <isabbasso@...eup.net>; Vlastimil Babka <vbabka@...e.cz>; Rasmus Villemoes <linux@...musvillemoes.dk>; linux-kernel@...r.kernel.org; linux-kbuild@...r.kernel.org; llvm@...ts.linux.dev
Betreff: Re: [PATCH] Makefile.debug: support for -gz=zstd

On Sun, Oct 23, 2022 at 8:46 AM Sedat Dilek <sedat.dilek@...il.com> wrote:
>
> On Thu, Oct 20, 2022 at 8:43 PM Nathan Chancellor <nathan@...nel.org> wrote:
> >
> > On Thu, Oct 20, 2022 at 10:56:49AM -0700, Nick Desaulniers wrote:
> > > +config DEBUG_INFO_UNCOMPRESSED
> > > +     bool "Don't compress debug information"
> > > +     help
> > > +       Don't compress debug info sections.
> > > +
> > >  config DEBUG_INFO_COMPRESSED
>
> Also, I prefer...
>
> DEBUG_INFO_COMPRESSED_NONE
> DEBUG_INFO_COMPRESSED_ZLIB
> DEBUG_INFO_COMPRESSED_ZSTD
>
> Following...
>
> $ ld.lld-16 -v
> Debian LLD 16.0.0 (compatible with GNU linkers)
>
> $ ld.lld-16 --help | grep compress-debug-sections  
> --compress-debug-sections=[none,zlib,zstd]

It's a good suggestion, though I deliberately did not modify the identifier used for the existing DEBUG_INFO_COMPRESSED.  No defconfigs set DEBUG_INFO_COMPRESSED explicitly, but I think one issue with changing the identifier of existing kconfigs is that upon upgrading to newer kernel sources, if you run `make oldmodconfig` if you previously had DEBUG_INFO_COMPRESSED=y, kconfig doesn't know that that option has been renamed to DEBUG_INFO_COMPRESSED_ZLIB so it would be silently disabled, and image sizes would increase due to uncompressed debug info. That seems developer hostile.

Masahiro, what are your thoughts on how to proceed? Should I change the pre-existing Kconfig identifier, or "let sleeping dogs lie?"

***

Cannot say what happens when CONFIG_XXX changes - I have not played with your patch.

Perhaps, we can use CONFIG_ DEBUG_INFO_COMPRESSED="none|zlib|zstd" with default: "none"?

-Sedat-