[PATCH] purgatory: Change default sha256 optimization to -O2

[Pratyush Anand]

On Thu, Nov 24, 2016 at 1:23 PM, Simon Horman <horms at verge.net.au> wrote:
> On Wed, Nov 23, 2016 at 09:57:09AM -0800, Geoff Levand wrote:
>> Change the default purgatory sha256 code optimization from -O0 to -O2, and add a
>> new arch specific makefile variable $(ARCH)_PURGATORY_SHA256_CFLAGS which can
>> over ride this default.  Set ia64_PURGATORY_SHA256_CFLAGS to -O0 to retain the
>> previous optimization level for ia64.
>>
>> The purgatory sha256 code needs the be built with -O0 for the  ia64
>> architecture.  Currently this code is built with -O0 for all architectures,
>> which slows down the calculations for architectures which could otherwise
>> use -O2.
>
> Could you give an indication of the performance improvement you expect,
> e.g. on arm64?
>

It takes around 20 second to verify SHA in purgatory when vmlinuz
image is around 13MB and initramfs is around 30M with -O2 enables.
Otherwise, it takes more than 2 minutes.

~Pratyush


>> Signed-off-by: Geoff Levand <geoff at infradead.org>
>> ---
>>  purgatory/Makefile           | 4 +---
>>  purgatory/arch/ia64/Makefile | 4 ++++
>>  2 files changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/purgatory/Makefile b/purgatory/Makefile
>> index ca0443c..328904e 100644
>> --- a/purgatory/Makefile
>> +++ b/purgatory/Makefile
>> @@ -38,9 +38,7 @@ clean += $(PURGATORY_OBJS) $(PURGATORY_DEPS) $(PURGATORY)
>>  -include $(PURGATORY_DEPS)
>> -# sha256.c needs to be compiled without optimization, else
>> -# purgatory fails to execute on ia64.
>> -purgatory/sha256.o: CFLAGS += -O0
>> +purgatory/sha256.o: CFLAGS += -O2 $($(ARCH)_PURGATORY_SHA256_CFLAGS)
>>  purgatory/sha256.o: $(srcdir)/util_lib/sha256.c
>>       mkdir -p $(@D)
>> diff --git a/purgatory/arch/ia64/Makefile b/purgatory/arch/ia64/Makefile
>> index 32c3d97..4a2564c 100644
>> --- a/purgatory/arch/ia64/Makefile
>> +++ b/purgatory/arch/ia64/Makefile
>> @@ -8,6 +8,10 @@ ia64_PURGATORY_SRCS += purgatory/arch/ia64/vga.c
>>  ia64_PURGATORY_EXTRA_CFLAGS = -ffixed-r28
>> +# sha256.c needs to be compiled without optimization, else
>> +# purgatory fails to execute on ia64.
>> +ia64_PURGATORY_SHA256_CFLAGS = -O0
>> +
>>  dist += purgatory/arch/ia64/Makefile $(ia64_PURGATORY_SRCS)  \
>>       purgatory/arch/ia64/io.h purgatory/arch/ia64/purgatory-ia64.h
>> --
>> 2.7.4
>>