On Wed, Jul 30, 2014 at 08:50:18PM +0200, Andi Kleen wrote: > From: Andi Kleen <ak@xxxxxxxxxxxxxxx> > > 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) > > v2: various fixes from Dirk Gouders. Improve commit message slightly. > v3: Fix clean rules and improve Kconfig slightly > v4: Fix merge error in last version (Sam Ravnborg) > Clarify description that it mainly helps disk size. > Cc: Dirk Gouders <dirk@xxxxxxxxxxx> > Cc: mmarek@xxxxxxx > Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx> Acked-by: Sam Ravnborg <sam@xxxxxxxxxxxx> > --- > .gitignore | 1 + > Makefile | 5 +++++ > lib/Kconfig.debug | 15 +++++++++++++++ > 3 files changed, 21 insertions(+) > > 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 > -- > 1.8.5.2 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
