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    SubjectRe: big picture UDP/IP performance question re 2.6.18 -> 2.6.32
    At 10:53 AM 10/5/2011 +0200, Eric Dumazet wrote:
    >Note :
    >Your results are from a combination of a user
    >application and kernel default strategies.
    >On other combinations, results can be completely different.
    >A wakeup strategy is somewhat tricky :
    >- Should we affine or not.
    >- Should we queue the wakeup on a remote CPU,
    > to keep scheduler data hot in a single cpu cache.
    >- Should we use RPS/RFS to queue the packet to
    > another CPU before even handling it in our stack,
    > to keep network data hot in a single cpu
    > cache. (check Documentation/networking/scaling.txt)
    >At least, with recent kernels, we have many
    >available choices to tune a workload.

    I would argue that results speak louder than
    features. A 300% deterioration in latency,
    600% deterioration in sigma latency and
    a 50-100% increase in apparent system overhead
    is not impressive.

    Our application is designed to run optimally
    as a scalable real-time network transaction
    processor and provides for a variety of
    different thread-pool and queuing approaches.
    Performance is worse for every one of them
    in newer kernels. The ones that scale the
    best fared worst.

    It seems to me that any scheduler-intensive
    application will suffer a similar fate.

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      Last update: 2011-10-05 14:01    [W:0.020 / U:9.720 seconds]
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