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Benchmarking Ubuntu's Low-Latency Kernel & Liquorix Post-Meltdown

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  • #11
    Originally posted by Linuxxx View Post
    - Use the deadline İO scheduler.

    - Use the 'performance' governor.

    - Additionally, if stuck on İntel, make sure to set the 'performance-bias' to '0'!
    How exactly do you do the above?

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    • #12
      Originally posted by Spooktra View Post

      How exactly do you do the above?
      see the x86_energy_perf_policy binary
      (shipped often in kernel-tools or similarly named packages)

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      • #13
        Originally posted by HenryM View Post
        Sure would be interesting if somebody could measure actual input latency in say CS:GO with a variety of hardware and software.
        Spectre/Meltdown appear to (mostly) not affect games.

        Or were you talking about Liquorix and kernel latency in general?

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        • #14
          The 'perf' test results vary by about three tenths of a millisecond over these kernels.
          I don't think that test says anything meaningful and it should be discarded as 'win' or a 'loss'.
          Time accounting precision in these kernels might vary by that amount (?) - anyone care to enlighten me on that thought.
          In a practical sense, 3 tenths of a ms wont keep us awake at night.
          $time ls /usr/bin varies by more. Does the test really do anything but return?

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          • #15
            Originally posted by LuukD View Post
            The 'perf' test results vary by about three tenths of a millisecond over these kernels.
            I don't think that test says anything meaningful and it should be discarded as 'win' or a 'loss'.
            Time accounting precision in these kernels might vary by that amount (?) - anyone care to enlighten me on that thought.
            In a practical sense, 3 tenths of a ms wont keep us awake at night.
            $time ls /usr/bin varies by more. Does the test really do anything but return?
            the Wins and Losses is a start, but as any statistic - it's a lie!
            I would like to see a programatic way to see if something won or loss by "an inch or a mile"

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            • #16
              Originally posted by Linuxxx View Post
              Here's how one can achieve real smoothness:

              - Use openSUSE Tumbleweed, since it contains the best Linux Kernel config by default. (250Hz tick timer, PREEMPT enabled)

              - Use the deadline İO scheduler.

              - Use the 'performance' governor.

              - Additionally, if stuck on İntel, make sure to set the 'performance-bias' to '0'!

              Now enjoy your silky-smooth Linux experience!
              using the performance governor is handy for some use cases, mainly since you'll avoid CPU scaling... but using it all the time seems like bad advice... especially on any device where you care about power-saving or temperatures ....

              and FYI, any desktop or mobile linux kernel is mostly going to be preempt. pretty standard stuff.

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              • #17
                Originally posted by Licaon View Post
                Spectre/Meltdown appear to (mostly) not affect games.

                Or were you talking about Liquorix and kernel latency in general?
                I mean in general. it would be very useful to compare a variety of AMD and Nvidia GPUs, driver and kernel combos, Linux vs Windows etc. and actual, effective latency, say, put a laser pointer on a mouse, measure mouse movement vs in-game monitor response with a high-speed camera...

                I found some results here: https://docs.google.com/spreadsheets...E-w/edit#gid=0

                some examples: GTX 970 averages 34ms (23-47ms), HD5770 was worse at about 47ms (36-56ms). both on an ASUS VG248QE monitor at 120Hz and Intel G4560 CPU.


                I guess this is all a bit off-topic, but the generic vs low-latency vs Liquorix comparisons got me going.

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                • #18
                  Originally posted by RelaxTrolls View Post

                  using the performance governor is handy for some use cases, mainly since you'll avoid CPU scaling... but using it all the time seems like bad advice... especially on any device where you care about power-saving or temperatures ....

                  and FYI, any desktop or mobile linux kernel is mostly going to be preempt. pretty standard stuff.
                  No need to worry, CPUs will still enter C-States!
                  Case in point: Even a passively cooled Notebook remains cool under normal usage.

                  Also, about this all being pretty standard stuff:
                  Go ahead and tell that to Red Hat (Fedora), Debian & Ubuntu!

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                  • #19
                    Originally posted by Spooktra View Post

                    How exactly do you do the above?
                    Performance governor:
                    Code:
                    cat << EOF | sudo tee /etc/systemd/system/performance.service
                    [Unit]
                    Description=CPU performance
                    
                    [Service]
                    Type=oneshot
                    ExecStart=/usr/bin/cpupower -c all frequency-set -g performance
                    
                    [Install]
                    WantedBy=multi-user.target
                    EOF
                    Damaged by Intel users only:
                    Code:
                    cat << EOF | sudo tee /etc/systemd/system/bias.service
                    [Unit]
                    Description=CPU bias
                    
                    [Service]
                    Type=oneshot
                    ExecStart=/usr/bin/cpupower -c all set --perf-bias 0
                    
                    [Install]
                    WantedBy=multi-user.target
                    EOF
                    After that:
                    Code:
                    sudo systemctl enable performance.service
                    
                    sudo systemctl enable bias.service
                    Now reboot!

                    For deadline IO scheduler, add this to your GRUB Kernel command line:
                    Code:
                    elevator=deadline
                    For BFQ, you need to add as well:
                    Code:
                    scsi_mod.use_blk_mq=1 elevator=bfq
                    You're welcome!

                    Comment


                    • #20
                      Originally posted by Linuxxx View Post

                      Performance governor:
                      Code:
                      cat << EOF | sudo tee /etc/systemd/system/performance.service
                      [Unit]
                      Description=CPU performance
                      
                      [Service]
                      Type=oneshot
                      ExecStart=/usr/bin/cpupower -c all frequency-set -g performance
                      
                      [Install]
                      WantedBy=multi-user.target
                      EOF
                      Damaged by Intel users only:
                      Code:
                      cat << EOF | sudo tee /etc/systemd/system/bias.service
                      [Unit]
                      Description=CPU bias
                      
                      [Service]
                      Type=oneshot
                      ExecStart=/usr/bin/cpupower -c all set --perf-bias 0
                      
                      [Install]
                      WantedBy=multi-user.target
                      EOF
                      After that:
                      Code:
                      sudo systemctl enable performance.service
                      
                      sudo systemctl enable bias.service
                      Now reboot!

                      For deadline IO scheduler, add this to your GRUB Kernel command line:
                      Code:
                      elevator=deadline
                      For BFQ, you need to add as well:
                      Code:
                      scsi_mod.use_blk_mq=1 elevator=bfq
                      You're welcome!
                      but ... You can do it much simplest and better and ... both clock 250 and 1000 are not such perfect solutions



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