| Message ID | 1406675493-2539-1-git-send-email-andi@firstfloor.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 2014-07-30 01:11, Andi Kleen wrote: > From: Andi Kleen <ak@linux.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 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) The failure mode with ccache is that the *.dwo files are not stored, but the build proceeds, right? This is at least what I'm seeing. I'm just wondering if the config option should be inverted to make all{yes,mod}config builds happy. But it's probably not necessary if the build passes. Thanks, Michal -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
> The failure mode with ccache is that the *.dwo files are not stored, but > the build proceeds, right? This is at least what I'm seeing. I'm just That's right. > wondering if the config option should be inverted to make > all{yes,mod}config builds happy. But it's probably not necessary if the > build passes. Ok I'll not change it then and only resend the other patch. -Andi -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/.gitignore b/.gitignore index f4c0b09..e213b27 100644 --- a/.gitignore +++ b/.gitignore @@ -34,6 +34,7 @@ *.gcno modules.builtin Module.symvers +*.dwo # # Top-level generic files diff --git a/Makefile b/Makefile index f3c543d..6a717cd 100644 --- a/Makefile +++ b/Makefile @@ -689,7 +689,11 @@ 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 @@ -1377,6 +1381,7 @@ clean: $(clean-dirs) @find $(if $(KBUILD_EXTMOD), $(KBUILD_EXTMOD), .) $(RCS_FIND_IGNORE) \ \( -name '*.[oas]' -o -name '*.ko' -o -name '.*.cmd' \ -o -name '*.ko.*' \ + -o -name '*.dwo' \ -o -name '.*.d' -o -name '.*.tmp' -o -name '*.mod.c' \ -o -name '*.symtypes' -o -name 'modules.order' \ -o -name modules.builtin -o -name '.tmp_*.o.*' \ diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 7a638aa..0360468 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -143,6 +143,21 @@ 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 significantly + reduces the build directory size for builds with DEBUG_INFO, + because it stores the information only once on disk in .dwo + files instead of multiple times in object files and executables. + In addition the debug information is also compressed. + + Requires recent gcc (4.7+) and recent gdb/binutils. + Any tool that packages or reads debug information would need + to know about the .dwo files and include them. + Incompatible with older versions of ccache. + config ENABLE_WARN_DEPRECATED bool "Enable __deprecated logic" default y