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The Performance Impact Of MDS / Zombieload Plus The Overall Cost Now Of Spectre/Meltdown/L1TF/MDS

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  • #41
    While software video rendering is CPU-intensive, it doesn't strike me as a task involving the kernel, unless data needs to be transferred to or from disk (which can usually be done in large chunks for video) or certain kinds of synchronization or memory allocation takes place.

    It's the cost of switching from user to kernel contexts and back again, and the protective methods designed to prevent against leaks of data throughout this process, which have caused the greatest impact. Those applications which must perform such activities tend to be the most-impacted.

    If you were running a task which did make such calls on threads running on the same cores as threads doing video rendering, it might also have a significant impact (potentially running worse than the 'no hyperthreading' case, as at least then it would run uninterrupted for longer periods of time, and have full use of the caches).

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    • #42
      openSUSE Tumbleweed

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      • #43
        Has anyone considered the power draw/battery performance with and without mitigations? While performance is going down, is it making the CPU more or less efficient?
        Also, what about thermals? Do the mitigation make a CPU run hotter, cooler, or is there no real difference?

        Both of the above factors are big factors in laptops/ultrabooks and other SFF machines.

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        • #44
          Originally posted by hydrian View Post
          Has anyone considered the power draw/battery performance with and without mitigations? While performance is going down, is it making the CPU more or less efficient?
          Also, what about thermals? Do the mitigation make a CPU run hotter, cooler, or is there no real difference?

          Both of the above factors are big factors in laptops/ultrabooks and other SFF machines.
          I've looked at it, power consumption is the same with/without the mitigations.
          Michael Larabel
          https://www.michaellarabel.com/

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          • #45
            Originally posted by xfcemint View Post

            Peak MIPS is a bad way to measure performance.

            Realistically, a 486-DX4 100 MHz is about 100x slower than a modern single-core. I did some research on this. And for multi-core, it doesn't make much sense to compare, like apples to oranges.
            Are you perhaps trashing the cache? I wonder because 100x is roughly the difference I see in my lock-less queue between a modern Xeon Platinum and a ARM A-53 (Rpi3B+) and the ARM is itself orders of magnitude faster than a 486.

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            • #46
              Originally posted by Michael View Post

              I've looked at it, power consumption is the same with/without the mitigations.
              the same for an entire task, or the same per unit of time? if it's per unit of time and a task takes 10% longer, the overal power consumption is higher.

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