Re: [PATCH] cksum: Use AVX2 and AVX512 for speedup

[Sam Russell]

I'm comfortable with enabling AVX512 by default. If we can find a CPU that
sets the VPCLMULQDQ flag but doesn't implement the VPCLMULQDQ opcode then
that's probably going to be an issue that affects much more coreutils.

On Tue, 26 Nov 2024 at 12:59, Pádraig Brady <P@draigbrady.com> wrote:

> On 26/11/2024 07:35, Sam Russell wrote:
> >  > However I don't see any changes in CFLAGS or builtin_cpu_supports()
> checks
> >  > between the first and this patch. Am I missing something?
> >
> > CFLAGS stayed the same because the compiler output is fine (my PC here
> doesn't have AVX512 but it has a recent gcc that can build AVX512
> instructions). It's possible the builtin_cpu_supports checks I used the
> first time were correct, but the latest patch is the result of checking
> intel manuals and the sanity checks against different servers.
>
> Sorry for the misunderstanding.
> I was worried about the SIGILL you encountered on the VM.
> Now I think what you are saying is there was no SIGILL with the adjusted
> cksum,
> and that issue was only with the less protected benchmarking code.
> So we should be good to enable the AVX512 code by default?
>
> thanks,
> Pádraig.
>