Messages in this thread | | | Date | Fri, 3 May 2013 18:02:52 +0900 | From | Kyungsik Lee <> | Subject | Re: [PATCH v3 -next 3/5] arm: Add support for LZ4-compressed kernel |
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On Tue, Apr 30, 2013 at 01:56:02PM -0700, Andrew Morton wrote: > On Tue, 5 Mar 2013 20:47:34 +0900 Kyungsik Lee <kyungsik.lee@lge.com> wrote: > > > This patch integrates the LZ4 decompression code to the arm pre-boot code. > > And it depends on two patchs below > > > > lib: Add support for LZ4-compressed kernel > > decompressor: Add LZ4 decompressor module > > > > ... > > > > - Apply CFLAGS, -Os to decompress.o to improve decompress > > performance during boot-up process > > > > ... > > > > --- a/arch/arm/boot/compressed/Makefile > > +++ b/arch/arm/boot/compressed/Makefile > > @@ -24,6 +24,9 @@ endif > > AFLAGS_head.o += -DTEXT_OFFSET=$(TEXT_OFFSET) > > HEAD = head.o > > OBJS += misc.o decompress.o > > +ifeq ($(CONFIG_KERNEL_LZ4),y) > > +CFLAGS_decompress.o := -Os > > +endif > > Surprised. You found that -Os produces faster code than -O2? Details, > please? -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.
Decompression Time(counts) UA -Os 6717 3447 -O2 6720 2728
Note: ARM v7, Kernel 3.4 counter freq. = 32768 HZ UA(Unaligned Access) gcc version 4.6.2 (Ubuntu/Linaro 4.6.2-14ubuntu2~ppa1)
Thanks, Kyungsik
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