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Commit 9012d011 authored by Masahiro Yamada's avatar Masahiro Yamada Committed by Linus Torvalds
Browse files

compiler: allow all arches to enable CONFIG_OPTIMIZE_INLINING 

Commit 60a3cdd0 ("x86: add optimized inlining") introduced
CONFIG_OPTIMIZE_INLINING, but it has been available only for x86.

The idea is obviously arch-agnostic.  This commit moves the config entry
from arch/x86/Kconfig.debug to lib/Kconfig.debug so that all
architectures can benefit from it.

This can make a huge difference in kernel image size especially when
CONFIG_OPTIMIZE_FOR_SIZE is enabled.

For example, I got 3.5% smaller arm64 kernel for v5.1-rc1.

  dec       file
  18983424  arch/arm64/boot/Image.before
  18321920  arch/arm64/boot/Image.after

This also slightly improves the "Kernel hacking" Kconfig menu as
e61aca51 ("Merge branch 'kconfig-diet' from Dave Hansen') suggested;
this config option would be a good fit in the "compiler option" menu.

Link: http://lkml.kernel.org/r/20190423034959.13525-12-yamada.masahiro@socionext.com


Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: default avatarBorislav Petkov <bp@suse.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Boris Brezillon <bbrezillon@kernel.org>
Cc: Brian Norris <computersforpeace@gmail.com>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Marek Vasut <marek.vasut@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Malaterre <malat@debian.org>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Stefan Agner <stefan@agner.ch>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent efc344c5

arch/x86/Kconfig

+0 −3
Original line number Diff line number Diff line
@@ -305,9 +305,6 @@ config ZONE_DMA32 
config AUDIT_ARCH

	def_bool y if X86_64



config ARCH_SUPPORTS_OPTIMIZED_INLINING

	def_bool y



config ARCH_SUPPORTS_DEBUG_PAGEALLOC

	def_bool y

arch/x86/Kconfig.debug

+0 −14
Original line number Diff line number Diff line
@@ -266,20 +266,6 @@ config CPA_DEBUG 
	---help---

	  Do change_page_attr() self-tests every 30 seconds.



config OPTIMIZE_INLINING

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

	---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

	  enabling this option will generate a smaller kernel there. Hopefully

	  this algorithm is so good that allowing gcc 4.x and above to make the

	  decision will become the default in the future. Until then this option

	  is there to test gcc for this.



	  If unsure, say N.



config DEBUG_ENTRY

	bool "Debug low-level entry code"

	depends on DEBUG_KERNEL

include/linux/compiler_types.h

+1 −2
Original line number Diff line number Diff line
@@ -140,8 +140,7 @@ struct ftrace_likely_data { 
 * Do not use __always_inline here, since currently it expands to inline again

 * (which would break users of __always_inline).

 */

#if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \

	!defined(CONFIG_OPTIMIZE_INLINING)

#if !defined(CONFIG_OPTIMIZE_INLINING)

#define inline inline __attribute__((__always_inline__)) __gnu_inline \

	__maybe_unused notrace

#else

lib/Kconfig.debug

+14 −0
Original line number Diff line number Diff line
@@ -318,6 +318,20 @@ config HEADERS_CHECK 
	  exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in

	  your build tree), to make sure they're suitable.



config OPTIMIZE_INLINING

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

	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

	  enabling this option will generate a smaller kernel there. Hopefully

	  this algorithm is so good that allowing gcc 4.x and above to make the

	  decision will become the default in the future. Until then this option

	  is there to test gcc for this.



	  If unsure, say N.



config DEBUG_SECTION_MISMATCH

	bool "Enable full Section mismatch analysis"

	help