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    SubjectRe: tbench regression with 2.6.33-rc1
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    On Fri, 2009-12-25 at 19:11 +0800, Lin Ming wrote:
    > Hi,
    >
    > Test machine: 16 cpus (4P/2Core/HT), 8G mem
    > tbench test command:
    > tbench_srv &
    > tbench 32
    >
    > Compared with 2.6.32, tbench has ~4% regression in 2.6.33-rc1.
    >
    > >From vmstat data, the context switch number also drop ~4%.
    > perf top data does not show much differences.
    >
    > But lockstat data shows huge difference in rq->lock, as below.
    > See the attachment for the full lockstat data.
    >
    > Any clue of this regression?

    Nope, I thought to see the same on a dual-socket machine, but when
    bisecting I ended up on a user-space perf commit, which is pretty much
    impossible.

    I did notice some variance in the numbers between boots, maybe it was
    large enough to fool me.. (~2800 MB/s was the good one, ~2200 MB/s was
    the bad one).

    perf itself also didn't really provide clue, perf record -ag on the
    workload didn't really show anything scheduler related. vmstat 1 did
    show a proportional drop in context switch rate between the kernels
    though.. most odd.





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