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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:
Steven J. Magnani <steve@digidescorp.com> Signed-off-by:
David S. Miller <davem@davemloft.net>
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