[PATCH -next 1/2] arm: Remove enforced Os flag for LZ4 decompressor

Kyungsik Lee
2013-05-06T08:42:54Z

-Os is enforced here, based on the test result of decompression time
below, slightly faster than -O2.

But further tests with UA show that using -O2 will be the right choice
especially in the case of the unaligned access enabled and the gap,
few counts in the normal decompression mode is small enough to remove -Os.

Decompression Time(counts)
Normal UA enabled
-Os 6717 3447
-O2 6720 2728

Note: ARM v7, Kernel 3.4
counter freq. = 32768 HZ
UA(Unaligned Access)
gcc version 4.6.2

Signed-off-by: Kyungsik Lee <kyungsik.lee@lge.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Florian Fainelli <florian@openwrt.org>
Cc: Yann Collet <yann.collet.73@gmail.com>
---
arch/arm/boot/compressed/Makefile | 3 ---
1 file changed, 3 deletions(-)

diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index 001a13a..198a4ad 100644
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -27,9 +27,6 @@ OBJS += misc.o decompress.o
ifeq ($(CONFIG_DEBUG_UNCOMPRESS),y)
OBJS += debug.o
endif
-ifeq ($(CONFIG_KERNEL_LZ4),y)
-CFLAGS_decompress.o := -Os
-endif
FONTC = $(srctree)/drivers/video/console/font_acorn_8x8.c

# string library code (-Os is enforced to keep it much smaller)
--
1.8.1.1