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    SubjectRe: [profile] amortize atomic hit count increments
    William Lee Irwin III <wli@holomorphy.com> wrote:
    >
    > read_proc_profile()
    > does not flush the per-cpu hashtables because flushing may cause
    > timeslice overrun on the systems where prof_buffer cacheline bounces
    > are so problematic as to livelock the timer interrupt.

    That's a bit of a problem, isn't it? As we can accumulate an arbitrarily
    large number of hits within the hash table is it not possible that the
    /proc/profile results could be grossly inaccurate?

    If you had two front-ends per cpu to the profiling buffer then the CPU
    which is running the /proc/profile read could tell all the other CPUs to
    flip to their alternate buffer and can then perform accumulation at its
    leisure.

    How does oprofile get around this? I guess in most modes the CPUs are not
    synchronised.

    One wonders how long we should keep flogging the /prof/profile profiling
    code. What systems are seeing this livelock?
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