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Linux 4.15 I/O Scheduler Tests: BFQ, CFQ, Kyber

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  • Linux 4.15 I/O Scheduler Tests: BFQ, CFQ, Kyber

    Phoronix: Linux 4.15 I/O Scheduler Tests: BFQ, CFQ, Kyber

    With some BFQ performance fixes included as part of Linux 4.15 along with other I/O scheduler work and block improvements for this latest Linux kernel series, here are some fresh benchmarks of the different I/O scheduler options using the Linux 4.15 Git kernel.

    http://www.phoronix.com/vr.php?view=25646

  • #2
    In openSUSE you can set the value from Yast, I on the notebook with ssd I set Noop, while on the desktop with HD I set cfq.

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    • #3
      What's BFQ low_latency supposed to be? The low_latency tunable is enabled by default, what else is there?

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      • #4
        Isn't BFQ supposed to prefer interactivity (avoiding UI freezes and such) instead of performance?

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        • #5
          Originally posted by RealNC View Post
          Isn't BFQ supposed to prefer interactivity (avoiding UI freezes and such) instead of performance?
          It is indeed, hence the tests about startup time under load.

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          • #6
            Originally posted by Charlie68 View Post
            In openSUSE you can set the value from Yast, I on the notebook with ssd I set Noop, while on the desktop with HD I set cfq.
            CFQ is SSD aware for years already, stop using NOOP just because "it sounds better"

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            • #7
              Does it sound better?
              https://doc.opensuse.org/documentati...tuning.io.html

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              • #8
                Where and how can you check what scheduler you're using? And then how can you change that if you wanted to ?

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                • #9
                  Code:
                  cat /sys/block/sdX/queue/scheduler
                  echo <SCHEDULER> > /sys/block/sdX/queue/scheduler
                  You can change the scheduler permanently by using
                  Code:
                  elevator=<SCHEDULER>
                  in your kernel parameters.

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                  • #10
                    I'm leaving BFQ disabled for now after what happened with kernel 4.12 when it was first enabled. After a suspend/resume cycle the system would become unusable due to all io related syscalls hanging. It turned out nobody had tested how the new code interacted with suspend/resume, despite the fact that the power-management features implemented at the time were known to be stubbed out. I believe this was fixed in 4.14, but it does not instil in me great faith that the kernel devs can prevent potentially filesystem-corrupting bugs from slipping through the net in the future.

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