> I could've sworn I heard the stack was single-copy
> on both the TX and RX sides. But, it doesn't look to
> me like it is. Rather, it looks like there is one copy
> in tcp_rcv_estabilshed() (via tcp_copy_to_iovec()), and a
> second copy in tcp_recvmsg() (which is called when the
> user calls read()). Both of these copies are, I believe,
> done by skb_copy_datagram_iovec().
tcp_recvmsg() only does the copy from the receive_queue
or the backlog queue. tcp_rcv_established() does the copy
directly into the iovec or queues it onto the receive_queue
or backlog queue for tcp_recvmsg() to complete the work. So
there arent two copies of the same data happening, just a
question of one or the other function doing the work depending
on whether there is currently a process doing a read or not..
hth,
thanks,
Nivedita
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This archive was generated by hypermail 2b29 : Mon Jul 15 2002 - 22:00:17 EST