• Steven J. Magnani's avatar
    NET_DMA: free skbs periodically · 73852e81
    Steven J. Magnani authored
    Under NET_DMA, data transfer can grind to a halt when userland issues a
    large read on a socket with a high RCVLOWAT (i.e., 512 KB for both).
    This appears to be because the NET_DMA design queues up lots of memcpy
    operations, but doesn't issue or wait for them (and thus free the
    associated skbs) until it is time for tcp_recvmesg() to return.
    The socket hangs when its TCP window goes to zero before enough data is
    available to satisfy the read.
    
    Periodically issue asynchronous memcpy operations, and free skbs for ones
    that have completed, to prevent sockets from going into zero-window mode.
    Signed-off-by: default avatarSteven J. Magnani <steve@digidescorp.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    73852e81
tcp.c 85.5 KB