Kbuild: Add option to set -femit-struct-debug-baseonly (d6f4ceb7) · Commits · 戴 / test

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@linux.intel.com> [mmarek: reformatted help text] Signed-off-by:

Michal Marek <mmarek@suse.cz>

Makefile

+4 −0

Original line number	Diff line number	Diff line
		@@ -557,6 +557,10 @@ 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

lib/Kconfig.debug

+13 −0

Original line number	Diff line number	Diff line
		@@ -595,6 +595,19 @@ 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.

		config DEBUG_VM
		bool "Debug VM"
		depends on DEBUG_KERNEL

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