On Tue, Apr 4, 2023 at 3:38 AM Zbigniew Jędrzejewski-Szmek <zbys...@in.waw.pl> wrote: > > 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. >
This is further confirmed by Arch's data that even x86_64-v3 isn't necessarily great either: https://sunnyflunk.github.io/2023/01/15/x86-64-v3-Mixed-Bag-of-Performance.html It seems that moving to -O3 would provide more gains than x86_64-v3. Otherwise, the only thing you really get from moving subarches is breaking lots of hardware. -- 真実はいつも一つ！/ Always, there's only one truth! _______________________________________________ devel mailing list -- devel@lists.fedoraproject.org To unsubscribe send an email to devel-le...@lists.fedoraproject.org Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org Do not reply to spam, report it: https://pagure.io/fedora-infrastructure/new_issue
