Linus Torvalds Comes Out Against "Completely Broken" x86_64 Feature Levels

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts
  • phoronix
    Administrator
    • Jan 2007
    • 67079

    Linus Torvalds Comes Out Against "Completely Broken" x86_64 Feature Levels

    Phoronix: Linus Torvalds Comes Out Against "Completely Broken" x86_64 Feature Levels

    With the new Linux kernel patches posted yesterday for cleaning up x86 32-bit kernels on x86_64 CPUs as part of that patch series was introducing new Kconfig build options around the x86_64 micro-architecture feature levels. It turns out though that Torvalds is completely against how the x86_64 feature levels are handled by the compiler toolchain folks and doesn't want to see it invading the kernel...

    Phoronix, Linux Hardware Reviews, Linux hardware benchmarks, Linux server benchmarks, Linux benchmarking, Desktop Linux, Linux performance, Open Source graphics, Linux How To, Ubuntu benchmarks, Ubuntu hardware, Phoronix Test Suite
  • rene
    Senior Member
    • Jul 2015
    • 1484

    #2
    finally, I told you so for years since this not reality matching nonsense was introduced, ... https://www.youtube.com/watch?v=-bmeuRIARQc

    Comment

    • mxan
      Senior Member
      • Jun 2022
      • 278

      #3
      "I have no idea who came up with the "microarchitecture levels" garbage, but as far as I can tell, it's entirely unofficial, and it's a completely broken model."

      Intel themselves created it, along with AMD, Red Hat and SUSE...

      Find out why Red Hat recommends building Red Hat Enterprise Linux 9 for x86-64-v2 and what you can expect from this new, optional microarchitecture level.

      Comment

      • mxan
        Senior Member
        • Jun 2022
        • 278

        #4
        Originally posted by rene View Post
        finally, I told you so for years since this not reality matching nonsense was introduced, ... https://www.youtube.com/watch?v=-bmeuRIARQc
        No one in the real world cares about obscure implementation details. Compiling for more advanced instructions available on newer processors = faster distro and faster software, it's really that simple. Linux can't be hamstrung by ancient hardware forever, that's what NetBSD is for.

        Comment

        • carewolf
          Senior Member
          • Nov 2012
          • 2255

          #5
          I mean by all means get rid of v4, it was always speculation, and reality has gone a different direction. But v2, and v3 are somewhat useful outside of the kernel.

          Comment

          • davidbepo
            Senior Member
            • Nov 2014
            • 935

            #6
            a sensible simplification for ISA optimization levels is introduced in collaboration with the creators of the ISA itself and successfully used in many actual applications
            Linus: REEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE

            Comment

            • avis
              Senior Member
              • Dec 2022
              • 2154

              #7
              Where is CoC(k)?

              Why is Linus still committing to the kernel? Oh, wait, without him everything will fall apart.

              Comment

              • patrick1946
                Senior Member
                • Sep 2021
                • 348

                #8
                Originally posted by mxan View Post
                "I have no idea who came up with the "microarchitecture levels" garbage, but as far as I can tell, it's entirely unofficial, and it's a completely broken model."

                Intel themselves created it, along with AMD, Red Hat and SUSE...

                https://developers.redhat.com/blog/2...itecture-level
                I think he was again not in context. The micro architecture levels are an useful simplification to generate few optimized binaries. The kernel is not using this features. Other software is!

                Comment

                • patrick1946
                  Senior Member
                  • Sep 2021
                  • 348

                  #9
                  Originally posted by carewolf View Post
                  I mean by all means get rid of v4, it was always speculation, and reality has gone a different direction. But v2, and v3 are somewhat useful outside of the kernel.
                  Actually v4 was useful until Intel could not get their little cores up to that level.

                  Comment

                  • ms178
                    Senior Member
                    • Sep 2018
                    • 1701

                    #10
                    Florian Weimer must be sad about Linus' comments, as he was spearheading this effort on the Glibc side.

                    And honestly, I don't get the logic of Linus here as march=native might be enough for individual users but not a suitable target from a distro perspective. These feature levels are meant to group certain CPU architectures from roughly the same era together. Yes, there are some rare exceptions but overall it would serve its purpose to lower the maintenance burden on the Kernel side while giving people with capable CPUs more instructions to work with with the potential to increase performance in some areas.

                    As far as I see it the good old graysky2 patch is still needed after this cleanup to be more flexible.
                    Last edited by ms178; 05 December 2024, 08:37 AM.

                    Comment

                    Working...
                    X