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    SubjectRe: [PATCH 2/2] perf_counter: optimize context switch between identical inherited contexts
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    On Fri, 2009-05-22 at 14:27 +1000, Paul Mackerras wrote:
    >
    > -----Unmodified----- With this patch series
    > Counters: none 2 HW 4H+4S none 2 HW 4H+4S
    >
    > 2 processes:
    > Average 3.44 6.45 11.24 3.12 3.39 3.60
    > St dev 0.04 0.04 0.13 0.05 0.17 0.19
    >
    > 8 processes:
    > Average 6.45 8.79 14.00 5.57 6.23 7.57
    > St dev 1.27 1.04 0.88 1.42 1.46 1.42
    >
    > 32 processes:
    > Average 5.56 8.43 13.78 5.28 5.55 7.15
    > St dev 0.41 0.47 0.53 0.54 0.57 0.81

    Any clues as to why the time is still dependent on the number of
    counters in the context? The approach seems to be O(1) in that it
    does a simple counter context swap on sched_out and nothing on sched_in.





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