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The Linux 3.8 Kernel Can Save A Lot Of RAM

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  • The Linux 3.8 Kernel Can Save A Lot Of RAM

    Phoronix: The Linux 3.8 Kernel Can Save A Lot Of RAM

    For certain workloads with the Linux 3.8 kernel the physical memory usage is lowered by a significant amount thanks to improvements within this kernel that's presently under development...

    http://www.phoronix.com/vr.php?view=MTI1MTQ

  • #2
    During testing I noticed big (up to 2.5 times) memory consumption overhead on some workloads (e.g. ft.A from NPB) if THP is enabled. The main reason for that big difference is lacking zero page in THP case. We have to allocate a real page on read page fault...With thp-never RSS is about 400k, but with thp-always it's 200M. After the patcheset thp-always RSS is 400k too.
    If I understand this correctly, it won't make my Firefox/Opera/Chrome take less memory...

    Still a nearly thousand-fold memory footprint reduction is quite large

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    • #3
      I could do with a little more RAM usage if performance is improved.

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      • #4
        Originally posted by mayankleoboy1 View Post
        I could do with a little more RAM usage if performance is improved.
        400k vs 200m is not a little more but 512x more. Also this shouldn't infect performance as before it simply reserved more RAM than needed. That's at least what I understand, correct me if I'm wrong.

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        • #5
          This is good news but I couldn't understand neither how exactly it achieved, nor to which configuration it applies. So I asked Google Search, and surely enough, it has spit out an explanation of how and why it works: http://lwn.net/Articles/517465/

          Still not sure to which setups it's applicable, though.

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          • #6
            Oh, and here's how to check if it's applicable to you:

            cat /proc/meminfo | grep HugePages

            If there's any memory allocated as huge pages, that patch will save memory for you. If not, this won't change anything.

            Source: http://www.kernel.org/doc/Documentat...ugetlbpage.txt

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            • #7
              Perhaps 3.8 can save RAM in specific situations, but I don't like the massive power cost for Intel video introduced in xf86-video-intel 2.20.12 -- i.e. keeping the GPU out of power-saving mode, supposedly to fix tearing in SandyBridge (something I and other SB users have never experienced anyway.)

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