Re: cleanup the RAID6 P/Q library v3

[H. Peter Anvin]

On June 29, 2026 5:21:52 AM PDT, Christoph Hellwig <hch@xxxxxx> wrote:
>On Fri, Jun 26, 2026 at 05:52:18PM -0700, H. Peter Anvin wrote:
>> On 2026-05-19 01:24, Christoph Hellwig wrote:
>> > 
>> > raid6: rework registration of optimized algorithms
>> > 
>> >  - avx2 instead of avx512 is probably the right thing for no
>> >    benchmarking, but if it was intentional (it wasn't), that should
>> >    be document.  So I'll just switch back to the previous version to
>> >    keep the state of the art
>> 
>> It is unlikely to be the right thing *going forward*, though.
>> 
>> The very unfortunate performance inversion is likely model-specific. It is one
>> of those things where you largely would have to have a list of quirks :(
>
>Note that the default is still to benchmark the implementations.
>This is just about the case where the user explicitly disabled that
>benchmark-based selection.
>

The real issue though is that the benchmarking isn't really helpful, either. 

It has to do with power across the whole chip, so it perversely enough depends on what *else* is going on...