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Amazon Reflects On The Great Year For DAMON In The Linux Kernel

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  • Amazon Reflects On The Great Year For DAMON In The Linux Kernel

    Phoronix: Amazon Reflects On The Great Year For DAMON In The Linux Kernel

    Merged just over a year ago into the Linux kernel was DAMON as an Amazon-developed solution for monitoring data accesses. In the year since being merged, DAMON has continued to see more functionality added and new users and developers becoming involved with this data access monitoring...

    https://www.phoronix.com/news/DAMON-Linux-2022

  • #2
    So now Alexa can sell me a CPU upgrade without me even knowing I need one? NTY

    Joking aside, high performance metrics are so incredibly useful and this is nice to see.

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    • #3
      They need to support it with a Monitoring And Telemetry Transport, for remote monitoring. Together, the combination can be called MATT/DAMON.

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      • #4
        Originally posted by coder View Post
        They need to support it with a Monitoring And Telemetry Transport, for remote monitoring. Together, the combination can be called MATT/DAMON.
        Noice

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        • #5
          Is this used by anyone outside Amazon?

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          • #6
            I have it disabled in the kernel as it actually hurts standard desktop performance when enabled. That is probably less so on high corecount machines.

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            • #7
              Originally posted by FPScholten View Post
              I have it disabled in the kernel as it actually hurts standard desktop performance when enabled. That is probably less so on high corecount machines.
              This is concerning...

              How did You measure this?

              Also, is there a way to disable it either at boot / runtime or does one need to recompile the kernel with Amazon's DAMON disabled?

              Thanks for any answer in advance!

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              • #8
                Originally posted by Linuxxx View Post

                This is concerning...

                How did You measure this?

                Also, is there a way to disable it either at boot / runtime or does one need to recompile the kernel with Amazon's DAMON disabled?

                Thanks for any answer in advance!
                Measuring is somewhat crude, but with DAMON enabled on my laptop typical tasks like compiling or transcoding audio/video take a bit more time to complete. Also there appears to be a slight loss of responsiveness from the desktop. Have heard the same from other users. Damon in itself only does monitoring, it records usage and from that, optimisation can be derived for certain workloads or scenarios.

                Generally it is developed for use on (headless) servers and it definitely serves a purpose there. This is also more or less acknowledged in the DAMON documentation.

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                • #9
                  Originally posted by FPScholten View Post
                  Measuring is somewhat crude, but with DAMON enabled on my laptop typical tasks like compiling or transcoding audio/video take a bit more time to complete. Also there appears to be a slight loss of responsiveness from the desktop. Have heard the same from other users. Damon in itself only does monitoring, it records usage and from that, optimisation can be derived for certain workloads or scenarios.
                  Michael, if you're up for it, it'd be interesting to confirm or refute these findings.

                  FPScholten, can you confirm on which CPUs you've seen these effects? And you're running with mitigations enabled, right?

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                  • #10
                    I only tested this on my laptop with Haswell based intel 4710MQ cpu (4 cores 8 threads) and with mitigations off. As said, the kernel team evaluation of DAMON has the following line in it:
                    DAMON is lightweight. It increases system memory usage by 0.39% and slows target workloads down by 1.16%.

                    and in the design documents it says:
                    The monitoring overhead of this mechanism will arbitrarily increase as the size of the target workload grows.

                    So it is not unexpected that on relatively simple hardware such as laptops, running DAMON does indeed lead to noticeable effects. However, as it is developed by Amazon for their use on large datacenters and cloud services the overhead can easily be a tiny fraction of total computing capacity that is mitigated by the optimisation it can offer.

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