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Intel Resurrecting FSGSBASE Support For Linux To Help With Performance

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  • Intel Resurrecting FSGSBASE Support For Linux To Help With Performance

    Phoronix: Intel Resurrecting FSGSBASE Support For Linux To Help With Performance

    Going on for months had been work by Intel Linux developers on supporting the FSGSBASE instruction for helping Intel CPU performance going back to Ivybridge where this instruction set extension was first introduced. The FSGSBASE support was queued for the Linux 5.3 kernel but was reverted due to "serious bugs" in the implementation. Intel has now published a revised version of this support...

    http://www.phoronix.com/scan.php?pag...SE-Resurrected

  • perpetually high
    replied
    Heck yeah, more patches! I'm gonna be a guinea pig and give these a whirl on my Haswell machine.

    Looking through one of the patch diffs:

    - unsafe_fsgsbase [X86] Allow FSGSBASE instructions. This will be
    - replaced with a nofsgsbase flag.
    + nofsgsbase [X86] Disables FSGSBASE instructions.

    It looks like it's enabled by default with these patches, and you can use the nofsgsbase kernel parameter to disable it.

    EDIT: ran a couple preliminary Geekbench 5 benchmarks for a ballpark:

    with FSGSBASE:

    first run: 1138 single-core, 4051 multi-core
    second run: 1143 single-core, 4007 multi-core

    without FSGSBASE:

    first run: 1145 single-core, 4027 multi-core
    second run: 1145 single-core, 4005 multi-core

    All tests used the performance governor and were run with the command: nice -n -4 ./geekbench5
    Last edited by perpetually high; 09-12-2019, 09:20 PM.

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