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32-Bit Linux Prepares For Performance Hit Due To KPTI For Meltdown Mitigation

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  • 32-Bit Linux Prepares For Performance Hit Due To KPTI For Meltdown Mitigation

    Phoronix: 32-Bit Linux Prepares For Performance Hit Due To KPTI For Meltdown Mitigation

    Since January there has been KPTI in the x86_64 Linux kernel as Kernel-based Page Table Isolation for mitigating the Meltdown CPU vulnerability. On the back-burner since then has been KPTI support for the Linux x86 32-bit kernel to protect those using older 32-bit-only processors. With the upcoming Linux 4.19 kernel, KPTI is landing for Linux x86 32-bit. Here are sone benchmarks showing the performance penalty when upgrading to this new kernel on an Ubuntu i686 laptop.

    http://www.phoronix.com/vr.php?view=26626

  • #2
    Does this affect Tualatin?

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    • #3
      For some reason, this made me think of "If a tree falls in a forest..."

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      • #4
        Originally posted by NateHubbard View Post
        For some reason, this made me think of "If a tree falls in a forest..."
        you get free eggs from the bird nests that were on said tree?

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        • #5
          I think it does not matter while you can disable this patches. I spent a week using notebook with Core 2 Duo CPU and 64 bit Xubuntu as main working machine - disabling this fixes really helps with performance in many cases.

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          • #6
            Typo:

            Originally posted by phoronix View Post
            Here are sone benchmarks

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            • #7
              Originally posted by tildearrow View Post
              Typo:
              Maybe the benchmarks are Korean?
              https://www.urbandictionary.com/define.php?term=SONE

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              • #8
                Measurable, but not the end of the world.

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                • #9
                  Originally posted by Mark Rose View Post
                  Measurable, but not the end of the world.
                  You can also simply disable it at boot time with "nopti" argument to the kernel. So it's not an issue anyway, if you don't even care about it.

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                  • #10
                    Disabling via command-line does not strip out all the code; for best results you need to not compile all of it in the first place.

                    32-bit still has some relevance in the mini- and micro-VPS area even on 64-bit capable hardware where RAM is important. Kernel objects are much smaller on 32-bit - on the order of ~40% smaller for inodes, which can mean the ability to fit another 2/3 as many inodes in 1GB RAM, and more in cache as well. This is great when you have a large number of very small files to deal with, as can be the case when using nginx for a CDN. Obviously you need to consider the potential cost vs. benefit.

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