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Linux 5.0 Kernel Performance Is Sliding In The Wrong Direction

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  • Linux 5.0 Kernel Performance Is Sliding In The Wrong Direction

    Phoronix: Linux 5.0 Kernel Performance Is Sliding In The Wrong Direction

    With the Linux 5.0 kernel performance approaching the finish line, the past few days I've been ramping up my tests of this new kernel in our benchmarking farm. Unfortunately, when looking at the results at a macro level it's pointing towards Linux 5.0 yielding lower performance than previous kernel releases.

    http://www.phoronix.com/vr.php?view=27563

  • #2
    Is it possible there's something wonky with whatever is going into that PPA? I've compiled quite a few of my own linux- libre 5.0 rc kernels, and haven't noticed any difference between them and the 4.20 kernels I've been compiling. Of course, I haven't run any PTS benchmarks either.

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    • #3
      Would be good to script-compile v5 source using best parameters and compare to Ubuntu mainline v5 kernel.

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      • #4
        Would also be nice to test the latest 5.x with all mitigations turned off, to see if it can get back to 4.13 levels, or if this is with us for good.

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        • #5
          Some of these tests are producing very strange results that frankly don't make sense.

          e.g.

          NAS Parallel Benchmarks are about 20% slower after 4.12 - what would possibly account for that massive drop off?

          Stress-NG SysV Message passing, a giant nearly 2x increase from 4.12->4.13 and a similar-sized drop from 4.13->4.14.

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          • #6
            Originally posted by DanglingPointer View Post
            Would be good to script-compile v5 source using best parameters and compare to Ubuntu mainline v5 kernel.
            Yup. The problem could be on Ubuntu's side.

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            • #7
              I understand the difficulties related to bisecting the kernel looking for the commits related to the regressions and that investigating such wide spread issue would be too much to ask for without a supercomputer. However, the most extreme cases could hint at something, three in particular seem like good candidates for bisecting, sockperf latency under load, postgre buffer read-write and sockperf throughput.

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              • #8
                Or the fact the more complete a modern OS Linux becomes the more it can no longer be just a Server OS w/o tailoring it from the mainline kernel. You want all these modern services, well they come with a price.

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                • #9
                  This is why I am reluctant to upgrading from 4.18...

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                  • #10
                    https://freedesktop.org/wiki/Softwar...Optimizations/

                    "
                    16. Don't use debug kernels. Debug kernels are slow. Fedora exclusively uses debug kernels during the development phase of each release. If you care about boot performance, either recompile these kernels with debugging turned off
                    "

                    Plus use the 1000Hz timer and remove unneeded drivers and features from the kernel configuration. Kernel 5 is going to right direction, it has support for a lot of new hardware and is stable.
                    Code:
                    [email protected]:~$ inxi -bM
                    System:
                      Host: ryzenpc Kernel: 5.0.0-rc7 x86_64 bits: 64 Desktop: Xfce 4.12.4 
                      Distro: Debian GNU/Linux buster/sid 
                    Machine:
                      Type: Desktop Mobo: ASUSTeK model: PRIME B350M-K v: Rev X.0x 
                      serial: <root required> UEFI [Legacy]: American Megatrends v: 4207 
                      date: 12/07/2018 
                    CPU:
                      6-Core: AMD Ryzen 5 1600 type: MT MCP speed: 2957 MHz 
                    Graphics:
                      Device-1: AMD Ellesmere [Radeon RX 470/480] driver: amdgpu v: kernel 
                      Display: x11 server: X.Org 1.20.3 driver: amdgpu 
                      resolution: 3840x2160~60Hz 
                      OpenGL: 
                      renderer: Radeon RX 570 Series (POLARIS10 DRM 3.27.0 5.0.0-rc7 LLVM 7.0.1) 
                      v: 4.5 Mesa 19.1.0-devel (git-edbd2c1 2019-02-21 cosmic-oibaf-ppa)

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