Announcement

Collapse
No announcement yet.

Benchmarking The Intel Performance Change With Linux FSGSBASE Support

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • Benchmarking The Intel Performance Change With Linux FSGSBASE Support

    Phoronix: Benchmarking The Intel Performance Change With Linux FSGSBASE Support

    As covered last week, the Linux kernel is finally about to see FSGSBASE support a feature supported by Intel CPUs going back to Ivybridge and can help performance. Since that earlier article the FS/GS BASE patches have been moved to the x86/cpu branch meaning unless any last-minute problems arise the functionality will be merged for the Linux 5.3 cycle. I've also begun running some benchmarks to see how this will change the Linux performance on Intel hardware.

    http://www.phoronix.com/vr.php?view=27992

  • #2
    ethr (Server Address: localhost - Protocol: TCP - Test: Bandwidth - Threads: 32) looks weird...why is it faster with mitigations? Looks like a bug in the program.

    Comment


    • #3
      To put it into perspective, this reduces the 11.7% mitigation cost in average down to 8.8%.

      Comment


      • #4
        Wouldn't an older hardware benefit the most from this change? As it might not have any more recent feature to improve perf

        Comment


        • #5
          Originally posted by treba View Post
          ethr (Server Address: localhost - Protocol: TCP - Test: Bandwidth - Threads: 32) looks weird...why is it faster with mitigations? Looks like a bug in the program.
          Margin of error

          Comment


          • #6
            What about older chips (like ivy bridge) before any hardware mitigations? I assume modern Intel chips offset the performance hit from vulnerabilities with new hardware workarounds, something older chips can't do.

            Comment


            • #7
              If I understand it right, then AMD also supports FSGSBASE. Would love to see that benchmark run on a AMD CPU (@Michael).
              Regarding the spectre mitigation performance hits, they seem unrelated to FSGSBASE, so I don't think considerations like
              this reduces the 11.7% mitigation cost in average down to 8.8%
              are really relevant, since even with FSGSBASE the impact of mitigations is likely to remain 11.7%; As Michael wrote:
              Granted, FSGSBASE patches plus an unmitigated kernel would likely yield even better performance.
              They should be viewed independently as what they are:
              - FSGSBASE: a welcome performance improvement (at least for Intel, possibly AMD too?)
              - Spectre Mitigations: an annoying performance deterioration (esp. for Intel, somewhat for AMD too)

              Comment


              • #8
                Great that at least newer CPU owners get some free performance. And yes, AMD also supports this instruction, at least a quick and dirty Google search told me that for Zen 1. I'd like to see the performance impact on a couple of AMD CPUs, too.

                Comment


                • #9
                  FSGSBASE is supported on Ryzen, would be interesting to see if it makes any difference.

                  Comment


                  • #10
                    Can't wait to replace the last broken Intel CPU..

                    Comment

                    Working...
                    X