From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from todd.t-8ch.de (todd.t-8ch.de [159.69.126.157]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 593C570828; Sun, 1 Dec 2024 09:07:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=159.69.126.157 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733044062; cv=none; b=Y+4GRHBDT9NOzcggrsfUWQyQPxz3wSRE0sfMfzbploRIH5Xa5hdSGaOgvSEPW6H+AuLBFzMzu5E74NEsBCJgZSo1rcC8Lpv39MYhrKl04PrDWGZh2BcjszxSeVk/Pi+FpvrInf3LrTFMUYH4hDtzIr0PyAyWyzpuy2GgtcaGf3E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733044062; c=relaxed/simple; bh=tDyqJ+AboZTWobOGJf8LRbTQ3qYwmJ3f7oimo9myEF0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=I/aToRswnHCU97NLm/pUtbcWRZHQySdROzlUKXZteGStDEZ0wm3T7jeTx/n/AQ2gGOfYDz1AhTjOVsa8LltV0xmfJXLDNMNVxeChjtJhd09g09XlF1EXUT9RMp2F9i8LmLa2ZCSaL0w4hDEj0n4S179Z2I9dfuZ0XEpIzsSZvY0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=weissschuh.net; spf=pass smtp.mailfrom=weissschuh.net; dkim=pass (1024-bit key) header.d=weissschuh.net header.i=@weissschuh.net header.b=nWnPhViS; arc=none smtp.client-ip=159.69.126.157 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=weissschuh.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=weissschuh.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=weissschuh.net header.i=@weissschuh.net header.b="nWnPhViS" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=weissschuh.net; s=mail; t=1733043534; bh=tDyqJ+AboZTWobOGJf8LRbTQ3qYwmJ3f7oimo9myEF0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=nWnPhViSrmy+Dc3lyibeiuyLJXryBJqmq+wN5kWX59a0s969q3e4Xxs8JxVtB/SkN rio2k/7f20hyPz5LyJtfTaSX+WBoOKc8UAxiIPemszmurWuOU/FkpeMP8TsyyxKBSk IrPX3pAZEFzXXhbwz1e7bNQkXd0LS7S+24eMseL4= Date: Sun, 1 Dec 2024 09:58:54 +0100 From: Thomas =?utf-8?Q?Wei=C3=9Fschuh?= To: Nathan Chancellor Cc: Andrew Morton , Masahiro Yamada , linux-kernel@vger.kernel.org, Nicolas Schier , linux-kbuild@vger.kernel.org Subject: Re: [PATCH] kconfig: prefer toolchain default for debug information choice Message-ID: References: <20241124-kbuild-allconfig_debug_info-v1-1-07a7ac8d9a73@weissschuh.net> <20241125145251.GA2067874@thelio-3990X> <5fdad1e3-1b0c-4292-9bb1-2f7654d9b816@t-8ch.de> <20241125185837.GA495243@thelio-3990X> Precedence: bulk X-Mailing-List: linux-kbuild@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20241125185837.GA495243@thelio-3990X> On 2024-11-25 11:58:37-0700, Nathan Chancellor wrote: > On Mon, Nov 25, 2024 at 04:46:53PM +0100, Thomas Weißschuh wrote: > > On 2024-11-25 07:52:51-0700, Nathan Chancellor wrote: > > > On Sun, Nov 24, 2024 at 04:58:04PM +0100, Thomas Weißschuh wrote: > > > > Kconfig by default chooses the first entry of a choice setting. > > > > For the "debug information" choice this is DEBUG_INFO_NONE which > > > > disables debug information completely. > > > > > > > > The kconfig choice itself recommends to use "Toolchain default": > > > > > > > > Choose which version of DWARF debug info to emit. If unsure, > > > > select "Toolchain default". > > > > > > > > Align the actual configuration with the recommendation by providing an > > > > explicit default. > > > > > > > > This also enables more codepaths from allmodconfig/allyesconfig which > > > > depend on debug information being available. > > > > > > > > Signed-off-by: Thomas Weißschuh > > > > --- > > > > lib/Kconfig.debug | 1 + > > > > 1 file changed, 1 insertion(+) > > > > > > > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > > > > index 5d9eca035d470f7ba0c5ff932c37fd5869174269..0aefcd103d9012cd8067e5594404358b0e977644 100644 > > > > --- a/lib/Kconfig.debug > > > > +++ b/lib/Kconfig.debug > > > > @@ -240,6 +240,7 @@ config AS_HAS_NON_CONST_ULEB128 > > > > choice > > > > prompt "Debug information" > > > > depends on DEBUG_KERNEL > > > > + default DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT > > > > help > > > > Selecting something other than "None" results in a kernel image > > > > that will include debugging info resulting in a larger kernel image. > > > > > > > > --- > > > > base-commit: 9f16d5e6f220661f73b36a4be1b21575651d8833 > > > > change-id: 20241124-kbuild-allconfig_debug_info-f7449ba15be6 > > > > > > > > Best regards, > > > > -- > > > > Thomas Weißschuh > > > > > > > > > > I am not the biggest fan of this because it appears to have around a 5% > > > penalty in compilation times when I benchmarked building allmodconfig > > > with and without this change. > > > > > > With LLVM 19.1.4: > > > > > > Benchmark 1: DEBUG_INFO_NONE > > > Time (mean ± σ): 715.858 s ± 0.531 s [User: 38038.311 s, System: 3718.784 s] > > > Range (min … max): 715.271 s … 716.307 s 3 runs > > > > > > Benchmark 2: DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT > > > Time (mean ± σ): 760.749 s ± 0.172 s [User: 40699.800 s, System: 3817.819 s] > > > Range (min … max): 760.617 s … 760.943 s 3 runs > > > > > > Summary > > > DEBUG_INFO_NONE ran > > > 1.06 ± 0.00 times faster than DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT > > > > > > With GCC 14.2.0: > > > > > > Benchmark 1: DEBUG_INFO_NONE > > > Time (mean ± σ): 830.524 s ± 0.342 s [User: 43901.642 s, System: 4515.917 s] > > > Range (min … max): 830.135 s … 830.777 s 3 runs > > > > > > Benchmark 2: DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT > > > Time (mean ± σ): 873.663 s ± 0.150 s [User: 46102.416 s, System: 4968.065 s] > > > Range (min … max): 873.565 s … 873.836 s 3 runs > > > > > > Summary > > > DEBUG_INFO_NONE ran > > > 1.05 ± 0.00 times faster than DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT > > > > > > I understand the desire to have CONFIG_DEBUG_INFO_BTF be selected with > > > allmodconfig for the sake of coverage but that is going to add up for > > > builders doing many builds a day. > > > > No argument on the increased cost. > > > > But it's called "allyesconfig" not "ciconfig". > > I do realize that technically it is a Kconfig "choice" which > > does not have a "yes" answer. However I think it does fit the spirit. > > Sure, I do not really disagree there. I more interpret allmodconfig and > allyesconfig to mean "build all code" not "build with every option > possible", which is a small distinction but meaningful in this case. Not > saying one is more correct than the other, just saying where I come from > :) FWIW SCHED_CLASS_EXT and some netfilter components also depend on debug info and are therefore currently not part of all{mod,yes}config. Looking at current trends I expect more subsystems to be in the same boat over time. The (small) BTF support code is also affected. > > > Maybe we could add a fragment to kernel/configs for easily flipping > > > this? Another alternative that I have thought about recently is allowing > > > developers to specify a directory that holds out of tree config > > > fragments (KBUILD_FRAGMENTS_DIR?) that would be searched like > > > kernel/configs and arch/*/configs, so that people could maintain their > > > own fragments for easily doing something like: > > > > > > allmodconfig debug_info_btf.config > > > > > > during configuration. Regardless though, if others find this new default > > > desirable, I am fine with it. > > > > The same could be used by the CI setups :-) > > > > There should be less CI setups than regular developers, they known more > > about special or expensive configuration quirks and they should already > > have logic to filter and customize build configurations. > > > > While I'm arguing here to accomodate for my personal laziness, I also do > > think that these are generally valid arguments. > > But if there if it's not convincing enough, I'll drop it. > > Yes, I think there is definitely a fine argument here. I am certainly > not here to block anything, just giving my opinion as someone who does a > lot of builds every day :) Thanks for your input! The general interest seems to be very limited. > > The out of tree fragments idea sounds personally useful but a bit > > inconsistent with the rest of kbuild. > > AFAIK there is nothing similar; for thing like CFLAGS etc. > > KCFLAGS in Makefile or Documentation/kbuild/kbuild.rst? Indeed. I meant for "similar" to mean "pointing to file locations outside of the source tree". But looking at it again, this is probably not a good argument. Having such a feature would also help us for the nolibc testsuite.