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    sock: MSG_ZEROCOPY notification coalescing · 4ab6c99d
    Willem de Bruijn 提交于
    In the simple case, each sendmsg() call generates data and eventually
    a zerocopy ready notification N, where N indicates the Nth successful
    invocation of sendmsg() with the MSG_ZEROCOPY flag on this socket.
    
    TCP and corked sockets can cause send() calls to append new data to an
    existing sk_buff and, thus, ubuf_info. In that case the notification
    must hold a range. odify ubuf_info to store a inclusive range [N..N+m]
    and add skb_zerocopy_realloc() to optionally extend an existing range.
    
    Also coalesce notifications in this common case: if a notification
    [1, 1] is about to be queued while [0, 0] is the queue tail, just modify
    the head of the queue to read [0, 1].
    
    Coalescing is limited to a few TSO frames worth of data to bound
    notification latency.
    Signed-off-by: NWillem de Bruijn <willemb@google.com>
    Signed-off-by: NDavid S. Miller <davem@davemloft.net>
    4ab6c99d
skbuff.c 132.5 KB