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    SubjectRe: [PATCH] Close small window for vsyscall time inconsistencies
    Thomas Gleixner <> writes:
    >> So instead of shooting in the dark, I'd suggest to collect some
    >> numbers first,
    > That's what we did and John's analysis of the problem is pretty
    > correct.

    The source of the problem is that RDTSC is not always 100% sync

    We debugged a similar problem a long time ago and in that case
    it was the CPU speculating around the RDTSC. That was stopped
    by adding the CPUIDs to sync the core.

    I would double check that the CPUIDs are still executed as needed
    on the systems showing the issue.

    (the code to turn that on and off is somewhat subtle and breaks occasionally)

    Also it was assumed at some point it wasn't needed on P4, but that turned
    out to be wrong later. Perhaps the enable logic is still not quite

    Or perhaps the CPUIDs need to be moved inside or outside the


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      Last update: 2008-04-07 13:33    [W:0.020 / U:14.020 seconds]
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