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    Subjectclocksources: order of preference
    Why is the TSC preferred to the HPET as a clocksource for the x86 
    architecture?

    "Understanding the Linux Kernel" states that the HPET is preferable to
    the TSC due to its richer architecture. Up to version 2.6.17.14,
    arch/i386/kernel/timers/timer.c also contained a comment to that effect
    and accordingly ranked the HPET before the TSC.

    This was changed when the new clocksource infrastructure was introduced
    with version 2.6.18. (The HPET clocksource received a rating of 250; the
    TSC, 300.)

    Preferring the TSC leads to problems when it is unstable. While this can
    be prevented by setting CONFIG_X86_TSC, certain distribution kernels
    (striving for compatibility) don't, resulting in soft lockups.

    Are there better reasons to prefer the TSC or may I submit a patch that
    swaps the respective ratings?

    Thanks for reading,
    - Philipp Kohlbecher

    Please CC me, I am not on the list.


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