On 07/14/2010 03:43 PM, Andi Kleen wrote: > Kbuild: Add option to set -femit-struct-debug-baseonly > > Newer gcc has a -femit-struct-debug-baseonly option that dramatically > reduces the size of object files with debug info. What it does > is to only emit type information for structures when the structures > are defined in the same file or in a header file. > > This means the type information for most headers are not included. > This is not good when the type information is actually > needed (e.g. with kgdb or systemtap) > > But often kernel hackers only care about line numbers and don't > need all the type information anyways. In this case setting > the option can be a big win: > > A build dir for a specific x86-64 configuration with gcc 4.5 > shrunk from 2.3G to 1.2G. The compilation was also nearly a minute > faster. > > Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx> > > --- > Makefile | 4 ++++ > lib/Kconfig.debug | 12 ++++++++++++ > 2 files changed, 16 insertions(+) > > Index: linux-2.6.34-ak/Makefile > =================================================================== > --- linux-2.6.34-ak.orig/Makefile > +++ linux-2.6.34-ak/Makefile > @@ -554,6 +554,10 @@ KBUILD_CFLAGS += -g > KBUILD_AFLAGS += -gdwarf-2 > endif > > +ifdef CONFIG_DEBUG_INFO_REDUCED > +KBUILD_CFLAGS += $(call cc-option, -femit-struct-debug-baseonly) > +endif > + > ifdef CONFIG_FUNCTION_TRACER > KBUILD_CFLAGS += -pg > endif > Index: linux-2.6.34-ak/lib/Kconfig.debug > =================================================================== > --- linux-2.6.34-ak.orig/lib/Kconfig.debug > +++ linux-2.6.34-ak/lib/Kconfig.debug > @@ -616,6 +616,18 @@ config DEBUG_INFO > > If unsure, say N. > > +config DEBUG_INFO_REDUCED > + bool "Reduce debugging information" > + depends on DEBUG_INFO > + help > + If you say Y here gcc is instructed to generate less debugging information > + for structure types. This means that tools that need full debugging information > + (like kgdb or systemtap) won't be happy. But if you merely need debugging > + information to resolve line numbers there is no loss. > + Advantage is that build directory object sizes shrink dramatically over > + a full DEBUG_INFO build and compile times are reduced too. > + Only works with newer gcc versions. > + I reformatted this help text to not wrap in a 80-column terminal and applied the patch to the kbuild tree. thanks, Michal -- 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
