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Commit 60a3cdd0 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

x86: add optimized inlining 



add CONFIG_OPTIMIZE_INLINING=y.

allow gcc to optimize the kernel image's size by uninlining
functions that have been marked 'inline'. Previously gcc was
forced by Linux to always-inline these functions via a gcc
attribute:

 #define inline	inline __attribute__((always_inline))

Especially when the user has already selected
CONFIG_OPTIMIZE_FOR_SIZE=y this can make a huge difference in
kernel image size (using a standard Fedora .config):

   text    data     bss     dec           hex filename
   5613924  562708 3854336 10030968    990f78 vmlinux.before
   5486689  562708 3854336  9903733    971e75 vmlinux.after

that's a 2.3% text size reduction (!).

Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent b1721d0d

arch/x86/Kconfig.debug

+13 −0
Original line number Diff line number Diff line
@@ -257,3 +257,16 @@ config CPA_DEBUG 
	  Do change_page_attr() self-tests every 30 seconds.



endmenu



config OPTIMIZE_INLINING

	bool "Allow gcc to uninline functions marked 'inline'"

	default y

	help

	  This option determines if the kernel forces gcc to inline the functions

	  developers have marked 'inline'. Doing so takes away freedom from gcc to

	  do what it thinks is best, which is desirable for the gcc 3.x series of

	  compilers. The gcc 4.x series have a rewritten inlining algorithm and

	  disabling this option will generate a smaller kernel there. Hopefully

	  this algorithm is so good that allowing gcc4 to make the decision can

	  become the default in the future, until then this option is there to

	  test gcc for this.

arch/x86/configs/i386_defconfig

+1 −0
Original line number Diff line number Diff line
@@ -1421,6 +1421,7 @@ CONFIG_DEBUG_BUGVERBOSE=y 
# CONFIG_DEBUG_VM is not set

# CONFIG_DEBUG_LIST is not set

# CONFIG_FRAME_POINTER is not set

CONFIG_OPTIMIZE_INLINING=y

# CONFIG_RCU_TORTURE_TEST is not set

# CONFIG_LKDTM is not set

# CONFIG_FAULT_INJECTION is not set

arch/x86/configs/x86_64_defconfig

+1 −0
Original line number Diff line number Diff line
@@ -1346,6 +1346,7 @@ CONFIG_DEBUG_BUGVERBOSE=y 
# CONFIG_DEBUG_VM is not set

# CONFIG_DEBUG_LIST is not set

# CONFIG_FRAME_POINTER is not set

CONFIG_OPTIMIZE_INLINING=y

# CONFIG_RCU_TORTURE_TEST is not set

# CONFIG_LKDTM is not set

# CONFIG_FAULT_INJECTION is not set

include/linux/compiler-gcc.h

+9 −3
Original line number Diff line number Diff line
@@ -28,9 +28,15 @@ 
#define __must_be_array(a) \

  BUILD_BUG_ON_ZERO(__builtin_types_compatible_p(typeof(a), typeof(&a[0])))



/*

 * Force always-inline if the user requests it so via the .config:

 */

#if !defined(CONFIG_OPTIMIZE_INLINING) && (__GNUC__ >= 4)

# define inline		inline		__attribute__((always_inline))

# define __inline__	__inline__	__attribute__((always_inline))

# define __inline	__inline	__attribute__((always_inline))

#endif



#define __deprecated			__attribute__((deprecated))

#define __packed			__attribute__((packed))

#define __weak				__attribute__((weak))