Re: [PATCH v2] genksyms: Support arm64 CRC32 hardware acceleration1~

[Petr Pavlu]

On 5/25/26 3:41 PM, Wentao Guan wrote:
>> On 5/25/26 10:02 AM, Wentao Guan wrote:
>>>> Additionally, many distributions already switched to gendwarfksyms last
>>>> year. Unless someone provides a good reason to keep genksyms around,
>>>> I expect it will be deprecated soon and eventually removed. It would be
>>>> more valuable to show whether the same optimization is worthwhile for
>>>> gendwarfksyms.
>>> I see gendwarfksyms use crc32 from <zlib.h>, which from zlib1g-dev and zlib1g.
>>
>> Ah, I forgot about this, so gendwarfksyms should already be well
>> optimized. I think that is the most important thing.
> 
> Which way do you prefer? There are two ways now:
> 1. this work,
> 2. import zlib like gendwarfksyms and remove the huge crctab,
> but need make sure any arch do not cause performance regression?
> (Assert the user libs precompile with +crc32 is right?)
> I do some early tests show that:
> 1) zlib in x86 fast than genksym software
> 2) zlib in arm64 debian precompile slow than genksym software(crc32 not in armv8)
> 3) zlib in arm64 recompile with +crc32 same speed with genksyms hardware

I think it would be useful to first have more data showing that the CRC
calculation in genksyms is a hot path and contributes significantly to
the overall kernel build time.

-- 
Thanks,
Petr