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 <linux@xxxxxxxxxxxxxx> > > > --- > > > 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 <linux@xxxxxxxxxxxxxx> > > > > > > > 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
