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authorAndi Kleen <ak@linux.intel.com>2014-07-30 20:50:18 +0200
committerMichal Marek <mmarek@suse.cz>2014-07-30 22:54:52 +0200
commit866ced950bcd54820c3e571229356adc2b2dd72e (patch)
tree13cd5b869ab355f7bd193aed1452d260b1165808
parent011bf1254772b20083b1bab53f3aa58b1ec95eb1 (diff)
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kbuild: Support split debug info v4
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@gouders.net> Signed-off-by: Andi Kleen <ak@linux.intel.com> Acked-by: Sam Ravnborg <sam@ravnborg.org> Signed-off-by: Michal Marek <mmarek@suse.cz>
-rw-r--r--.gitignore1
-rw-r--r--Makefile5
-rw-r--r--lib/Kconfig.debug15
3 files changed, 21 insertions, 0 deletions
diff --git a/.gitignore b/.gitignore
index f4c0b091dcf4..e213b27f3921 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 89fe23a0825c..e5a269465f99 100644
--- a/Makefile
+++ b/Makefile
@@ -684,7 +684,11 @@ 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
@@ -1372,6 +1376,7 @@ 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 7cfcc1b8e101..910355da9d14 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