Messages in this thread | | | Date | Wed, 18 Aug 2021 17:08:40 +0200 (CEST) | From | torvic9@mailbox ... | Subject | Re: [PATCH 2/2] x86, Makefile: Add new generic x86-64 settings v2/v3/v4 |
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> Borislav Petkov <bp@alien8.de> hat am 17.08.2021 20:36 geschrieben: > > > On Tue, Aug 17, 2021 at 04:24:48PM +0200, torvic9@mailbox.org wrote: > > Add new generic x86-64 CPU tunings introduced with recent versions of > > gcc and clang, as documented in x86-64-psABI [1]. > > > > This is taken straight from graysky's CPU optimization patch with minor > > modifications [2]. > > > > [1] https://gitlab.com/x86-psABIs/x86-64-ABI/-/commit/77566eb03bc6a326811cb7e9a6b9396884b67c7c > > [2] https://github.com/graysky2/kernel_compiler_patch > > > > Signed-off-by: Tor Vic <torvic9@mailbox.org> > > --- > > arch/x86/Kconfig.cpu | 26 +++++++++++++++++++++++++- > > arch/x86/Makefile.cpu | 6 ++++++ > > 2 files changed, 31 insertions(+), 1 deletion(-) > > > > diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu > > index 814fe0d349b0..a2c872aa5a0b 100644 > > --- a/arch/x86/Kconfig.cpu > > +++ b/arch/x86/Kconfig.cpu > > @@ -294,6 +294,30 @@ config GENERIC_CPU > > Generic x86-64 CPU. > > Run equally well on all x86-64 CPUs. > > > > +config GENERIC_CPU_V2 > > + bool "Generic-x86-64-v2" > > + depends on ( CC_IS_GCC && GCC_VERSION > 110000 ) || ( CC_IS_CLANG && CLANG_VERSION >= 120000 ) > > + depends on X86_64 > > + help > > + Generic x86-64 CPU. > > + Run equally well on all x86-64 CPUs with min support of x86-64-v2. > > + > > +config GENERIC_CPU_V3 > > + bool "Generic-x86-64-v3" > > + depends on ( CC_IS_GCC && GCC_VERSION > 110000 ) || ( CC_IS_CLANG && CLANG_VERSION >= 120000 ) > > + depends on X86_64 > > + help > > + Generic x86-64-v3 CPU with v3 instructions. > > + Run equally well on all x86-64 CPUs with min support of x86-64-v3. > > + > > +config GENERIC_CPU_V4 > > + bool "Generic-x86-64-v4" > > + depends on ( CC_IS_GCC && GCC_VERSION > 110000 ) || ( CC_IS_CLANG && CLANG_VERSION >= 120000 ) > > + depends on X86_64 > > + help > > + Generic x86-64 CPU with v4 instructions. > > + Run equally well on all x86-64 CPUs with min support of x86-64-v4. > > Every once in a while, patches like that pop up without any real numbers > advocating for the additional and perhaps unnecessary complexity. > > If those -march switches don't bring any measureable improvements - and > I highly doubt they do - you shouldn't waste time with submitting them.
Borislav, I ran some quick checks and benchmarks, and your doubts seem to be justified. A 5.14-rc6 kernel compiled with the default 'generic' and one built with 'x86-64-v3' even have the exact same uncompressed file size. Benchmarks were inconclusive as well. So I will only resubmit the first patch of this series, with the changes suggested by Masahiro and Christoph.
> > Thx. > > -- > Regards/Gruss, > Boris. > > https://people.kernel.org/tglx/notes-about-netiquette
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