On Tue, Apr 04, 2023 at 07:37:59AM +0000, Zbigniew Jędrzejewski-Szmek 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%.
Given that GCC 12 and later autovectorizes at -O2, it might be more than 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. Why a subrpm? Should be possible to just arrange for one src.rpm to build the library twice and install the x86-64-v3 into /usr/lib64/glibc-hwcaps/x86-64-v3/ Perhaps come with some macro to simplify that for packagers. Jakub _______________________________________________ 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
