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    Subject[PATCH V3 0/8] macvtap/vhost TX zero copy support
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    This patchset add supports for TX zero-copy between guest and host
    kernel through vhost. It significantly reduces CPU utilization on the
    local host on which the guest is located (It reduced 30-50% CPU usage
    for vhost thread for single stream test). The patchset is based on
    previous submission and comments from the community regarding when/how
    to handle guest kernel buffers to be released. This is the simplest
    approach I can think of after comparing with several other solutions.

    This patchset includes:

    1/8: Add a new sock zero-copy flag, SOCK_ZEROCOPY;

    2/8: Add a new device flag, NETIF_F_ZEROCOPY for lower level device
    support zero-copy;

    3/8: Add a new struct skb_ubuf_info in skb_share_info for userspace
    buffers release callback when lower device DMA has done for that skb;

    4/8: Add vhost zero-copy callback in vhost when skb last refcnt is gone;
    add vhost_zerocopy_add_used_and_signal to notify guest to release TX skb
    buffers.

    5/8: Add macvtap zero-copy in lower device when sending packet is
    greater than 128 bytes.

    6/8: Add Chelsio 10Gb NIC to zero copy feature flag

    7/8: Add Intel 10Gb NIC zero copy feature flag

    8/8: Add Emulex 10Gb NIC zero copy feature flag

    The patchset is built against most recent linux 2.6.git. It has passed
    netperf/netserver multiple streams stress test on above NICs.

    The single stream test results from 2.6.37 kernel on Chelsio:

    64K message size: copy_from_user dropped from 40% to 5%; vhost thread
    cpu utilization dropped from 76% to 28%

    I am collecting more test results against 2.6.39-rc3 kernel and will
    provide the test matrix later.

    Thanks
    Shirley




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