On Sun, Apr 02, 2023 at 09:54:04PM +0200, Dan Čermák wrote:
> The only benchmark that *I* am aware of is this one done by Martin
> Jambor: https://jamborm.github.io/spec-2022-07-29-levels/

This is very … underwhelming. x86-64-v2 is essentially identical to x86-64-v1.
x86-64-v3 is better. It even shows speed-ups of 20%, but only with -Ofast.
And -Ofast is not something that can be enabled as a default build flag,
because it leads to surprising and unpredictable behaviour in some cases. (*)
At -O2, which we use, the speed up is maybe 10%.

> tl;dr; v2 does not really bring notable improvements, only v3 but also
> only in some selected synthetic benchmarks.
> 
> openSUSE Tumbleweed went a different route and chose to utilize
> glibc-hwcaps instead:
> https://en.opensuse.org/openSUSE:X86-64-Architecture-Levels
> https://lists.opensuse.org/archives/list/fact...@lists.opensuse.org/thread/ZOHLT4CQ7TDOJJ2VV7HKMN5G2MR2CTMD

Yeah, I think that's the way to go. I think we should identify 100
shared libraries which would be positively impacted by x86-64-v3
and provide a -v3 subrpm for them. This would be a nice feature for
F40.

Zbyszek
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