On Tue, Apr 15, 2014 at 01:36:02PM +0200, Markus Trippelsdorf wrote: > On 2014.04.15 at 13:19 +0200, Sam Ravnborg wrote: > > > > > > And while the code size reduction is less for MIPS than what others have > > > reported for their platforms (I'm still investigating) is still is enough > > > that embedded developers would commit murder for. > > > > I have experimented a little with a patch that links all of vmlinux in one step. > > I compared the text size of vmlinux without and with -ffunction-sections. > > > > With a defconfig build on x86 (32 bit) I got following results: > > > > size difference > > singlelink 10266506 > > function-sections 9487369 779137 7,5% > > > > So this is a reduction of ~800 kb by enabling -ffunction-sections which > > allows the linker to throw away unused sections. > > > > I have not boot tested the kernel so chances are that too much was thrown out by the linker. > > But this is an option that has much smaller cost to use than lto. > > And seems to benefit nicely in size. > > > > I have not tried this wihtout my singlelink patch - but I assume similar results. > > No, it wouldn't work, because you cannot mix -r and --gc-sections (or > gold's --icf (identical code folding)). With make allnoconfig I see a 5% decrease in text size by applying -ffunction-sections. This is with latest mainline and no other than the following applied: diff --git a/arch/x86/Makefile b/arch/x86/Makefile index 602f57e..51bac0a 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -171,6 +171,8 @@ KBUILD_CFLAGS += -fno-asynchronous-unwind-tables KBUILD_CFLAGS += $(call cc-option,-mno-sse -mno-mmx -mno-sse2 -mno-3dnow,) KBUILD_CFLAGS += $(call cc-option,-mno-avx,) +KBUILD_CFLAGS += -ffunction-sections + KBUILD_CFLAGS += $(mflags-y) KBUILD_AFLAGS += $(mflags-y) What can then explain this size difference? Sam -- 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
