[PATCH 2/3] scripts: Select XZ --arm64 BCJ filter for 64-bit arm

[Ahmad Fatoum]

On 07.09.23 11:48, Jules Maselbas wrote:
> On Thu, Sep 07, 2023 at 10:56:21AM +0200, Ahmad Fatoum wrote:
>> On 06.09.23 17:08, Jules Maselbas wrote:
>>> This change will select the arm64 BCJ filter for aarch64 instead of
>>> the arm filter which was always selected for arm based architectures.
>>>
>>> The selected filter is also tested, by looking if it is present in
>>> the long help message of xz, this is because the arm64 BCJ filter is
>>> a recent addition to xz.
>>>
>>> Signed-off-by: Jules Maselbas <jmaselbas at zdiv.net>
>>
>> How much of an improvement is BCJ=--arm over BCJ=""?
> In my case using the --arm BCJ on a aarch64 barebox is slightly worst
> than no BCJ at all.

OK, that answers that question... :D

Reviewed-by: Ahmad Fatoum <a.fatoum at pengutronix.de>

> 
> $ xz -vkf --check=crc32 --lzma2=dict=32MiB barebox.bin
>   100 %        84.7 KiB / 236.9 KiB = 0.357
> $ xz -vkf --check=crc32 --arm --lzma2=dict=32MiB barebox.bin
>   100 %        85.5 KiB / 236.9 KiB = 0.361
> $ xz -vkf --check=crc32 --arm64 --lzma2=dict=32MiB barebox.bin
>   100 %        81.0 KiB / 236.9 KiB = 0.342
> 
> 
>> I wonder if we should fallback from --arm64 to --arm.
>>  
>> Cheers,
>> Ahmad
>>
>>> ---
>>>  scripts/xz_wrap.sh | 5 ++++-
>>>  1 file changed, 4 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/scripts/xz_wrap.sh b/scripts/xz_wrap.sh
>>> index 7a2d372f48..5b5f3adcff 100755
>>> --- a/scripts/xz_wrap.sh
>>> +++ b/scripts/xz_wrap.sh
>>> @@ -16,8 +16,11 @@ case $SRCARCH in
>>>  	x86)            BCJ=--x86 ;;
>>>  	powerpc)        BCJ=--powerpc ;;
>>>  	ia64)           BCJ=--ia64; LZMA2OPTS=pb=4 ;;
>>> -	arm)            BCJ=--arm ;;
>>> +	arm)            BCJ=--arm$S64 ;;
>>>  	sparc)          BCJ=--sparc ;;
>>>  esac
>>>  
>>> +# clear BCJ filter if unsupported
>>> +xz -H | grep -q -- $BCJ || BCJ=
>>> +
>>>  exec xz --check=crc32 $BCJ --lzma2=$LZMA2OPTS,dict=32MiB
>>
>> -- 
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>>
> 

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
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