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    Subject[RFC PATCH 0/1] vhost: Reduce TX used buffer signal for performance
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    This patch will change vhost TX used buffer guest signaling from one by
    one to 3/4 ring size. I have tried different size, like 4, 16, 1/4 size,
    1/2 size, and found that the large size is best for message size between
    256 - 4K with netperf TCP_STREAM test, so 3/4 of the ring size is picked
    up for signaling.

    Tested both UDP and TCP performance with guest 2vcpu. The 60 secs
    netperf run shows that guest to host performance for TCP.

    TCP_STREAM

    Message size Guest CPU(%) BW (Mb/s)
    before:after before:after

    256 57.84:58.42 1678.47:1908.75
    512 68.68:60.21 1844.18:3387.33
    1024 68.01:58.70 1945.14:3384.72
    2048 65.36:54.25 2342.45:3799.31
    4096 63.25:54.62 3307.11:4451.78
    8192 59.57:57.89 6038.64:6694.04

    UDP_STREAM
    1024 49.64:26.69 1161.0:1687.6
    2048 49.88:29.25 2326.8:2850.9
    4096 49.59:29.15 3871.1:4880.3
    8192 46.09:32.66 6822.9:7825.1
    16K 42.90:34.96 11347.1:11767.4

    For large message size, 60 secs run remains almost the same. I guess the
    signal might not play a big role in large message transmission.

    Shirley



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