[PATCH] x86: Don't set Prefer_No_AVX512 for processors with AVX512 and AVX-VNNI

[Thiago Macieira]

On Tuesday, 7 December 2021 07:52:44 PST H.J. Lu wrote:
> > Would it make sense to run more extensive tests, or should we wait for
> > someone with production silicon to show up?
> 
> GCC is a heavy user of memcpy/memset, which is a good proxy of
> ZMM load/store impact on CPU frequency.   We need to run the same
> test on a production Rocket Lake.

Can someone run the same test on an Ice Lake? That will also answer whether we 
should enable the same thing for ICL / ICX.

RKL is a Cypress Cove, so I'd expect it to have the same performance numbers 
as ICL's Sunny Cove. The data I have says that, in theory, we should not see a 
frequency drop for 512-bit memcpy / memset on ICL or TGL, but I haven't got 
experimental data confirming that. And I can't really run the benchmark test 
on a laptop with very poor thermal dissipation (freq drops to 1500 MHz all on 
its own).

If a good ICL has the drop, then I'd assume RKL will too.

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel DPG Cloud Engineering