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Message-Id: <1391966278-23036-1-git-send-email-andi@firstfloor.org> Date: Sun, 9 Feb 2014 18:17:58 +0100 From: Andi Kleen <andi@...stfloor.org> To: mmarek@...e.cz Cc: linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>, Dirk Gouders <dirk@...ders.net> Subject: [PATCH] kbuild: Support split debug info v2 From: Andi Kleen <ak@...ux.intel.com> This is an alternative approach to lower the overhead of debug info (as we discussed a few days ago) gcc 4.7+ and newer binutils have a new "split debug info" debug info model where the debug info is only written once into central ".dwo" files. This avoids having to copy it around multiple times, from the object files to the final executable. It also lowers the disk space requirements. In addition it defaults to compressed debug data. More details here: http://gcc.gnu.org/wiki/DebugFission This patch adds a new option to enable it. It has to be an option, because it'll undoubtedly break everyone's debuginfo packaging scheme. gdb/objdump/etc. all still work, if you have new enough versions. I don't see big compile wins (maybe a second or two faster or so), but the object dirs with debuginfo get significantly smaller. My standard kernel config (slightly bigger than defconfig) shrinks from 2.9G disk space to 1.1G objdir (with non reduced debuginfo). I presume if you are IO limited the compile time difference will be larger. Only problem I've seen so far is that it doesn't play well with older versions of ccache (apparently fixed, see https://bugzilla.samba.org/show_bug.cgi?id=10005) v2: various fixes from Dirk Gouders. Improve commit message slightly. Cc: Dirk Gouders <dirk@...ders.net> Signed-off-by: Andi Kleen <ak@...ux.intel.com> --- Makefile | 6 ++++++ lib/Kconfig.debug | 13 +++++++++++++ 2 files changed, 19 insertions(+) diff --git a/Makefile b/Makefile index 606ef7c..2f3d9d1 100644 --- a/Makefile +++ b/Makefile @@ -638,7 +638,11 @@ endif endif ifdef CONFIG_DEBUG_INFO +ifdef CONFIG_DEBUG_INFO_SPLIT +KBUILD_CFLAGS += $(call cc-option, -gsplit-dwarf, -g) +else KBUILD_CFLAGS += -g +endif KBUILD_AFLAGS += -Wa,--gdwarf-2 endif @@ -1072,6 +1076,8 @@ MRPROPER_FILES += .config .config.old .version .old_version $(version_h) \ extra_certificates signing_key.x509.keyid \ signing_key.x509.signer +CLEAN_FILES += .*.dwo + # clean - Delete most, but leave enough to build external modules # clean: rm-dirs := $(CLEAN_DIRS) diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index a48abea..367a6ba 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -143,6 +143,19 @@ config DEBUG_INFO_REDUCED DEBUG_INFO build and compile times are reduced too. Only works with newer gcc versions. +config DEBUG_INFO_SPLIT + bool "Produce split debuginfo in .dwo files" + depends on DEBUG_INFO + help + Generate debug info into separate .dwo files. This can be + faster for building than including the debug information directly + in the object files and the vmlinux, as it only needs to + be stored once to disk, not multiple times in object files. + Requires recent gcc (4.8+) and recent gdb/binutils. + Any tool that packages or reads debug information would need + to know about the .dwo files and include them. + Currently incompatible with ccache. + config ENABLE_WARN_DEPRECATED bool "Enable __deprecated logic" default y -- 1.8.5.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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