From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 047441B415F; Mon, 25 Nov 2024 18:58:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732561120; cv=none; b=SxtMftc13NeekILBVMMaUJGS0cA/85NyGxkTaHkoiWXVj92Tkz26rRRVRF/G7OJT1GBUy+GNpzFVOOzHCoIHooMbCDqpDwlAgslDyZmVyQyvf2N0R7aqhheCBARF5jAFd+haiifBb8VQHkEl32hxW3it4b6FpHn2bpRjY8Vht9Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732561120; c=relaxed/simple; bh=Fqrnpfc5wrMBhOgBDmW15TU9vQsVhq/EplZwpJQIS7s=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=fRal/d3G7dt1TKrKkbsMhUoePvzEtY7G9riTK4xVEc7QQK0D7ViV0X1/09BAO+ZQywOXQfHK6XNWRJefPF+fqMV4pBEuj2gvEZ8/XedpWdedYTzkZAeOhDKxf8l+OaIYuBkND+PmJHvIiKHlgBnIFXx9r2P3up2upgWBSNHADNE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YQnLt20d; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YQnLt20d" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0FA6AC4CECE; Mon, 25 Nov 2024 18:58:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1732561119; bh=Fqrnpfc5wrMBhOgBDmW15TU9vQsVhq/EplZwpJQIS7s=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=YQnLt20dC4rqMsXjR32O9xRjmTRZUv68cydjbF60dgZXotZON17lHJAmL8WMKk/Ic XSuQTw4u5ItMyV8Q2ji+WlKnn3o4qggMWMnXpqeRlYBNBF9sM27vOP8fkus2UWYDkV Qohq+zmWEtAkD11vRf8ZXyJdhi3i7ugOPbiGOGwisAFyTvFS6nHriX6QP98qNjx0lH z7hIpONn+ht5lDGIyGp5V+0EGEnEt9AZYKbxpqalXHDxG1QrVAvlUiqaSe5Us77HMa VAmSqZUhPieNjGk3ouYNz7t+9mn6/cZCDT88N3JroRTObe/S4v2AgdzLaJKZp+e8Gi 8BK5I8Minrzfg== Date: Mon, 25 Nov 2024 11:58:37 -0700 From: Nathan Chancellor To: Thomas =?iso-8859-1?Q?Wei=DFschuh?= 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: <20241125185837.GA495243@thelio-3990X> References: <20241124-kbuild-allconfig_debug_info-v1-1-07a7ac8d9a73@weissschuh.net> <20241125145251.GA2067874@thelio-3990X> <5fdad1e3-1b0c-4292-9bb1-2f7654d9b816@t-8ch.de> 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: <5fdad1e3-1b0c-4292-9bb1-2f7654d9b816@t-8ch.de> On Mon, Nov 25, 2024 at 04:46:53PM +0100, Thomas Weißschuh wrote: > Hi Nathan, > > 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 :) > > 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 :) > 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? Cheers, Nathan