Messages in this thread |  | | Date | Sun, 9 Jun 1996 01:34:52 +0100 | From | Pedro Roque Marques <> | Subject | Re: Speed of memcpy, csum_partial and csum_partial_copy |
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>>>>> "me" == Pedro Roque Marques <roque@di.fc.ul.pt> writes: >>>>> "Alan" == Alan Cox <alan@lxorguk.ukuu.org.uk> writes:
Alan> There are three for TCP loopback unless someone has fiddled Alan> recently. We copy:
sk_buff [with csum] sk_buff to sk_buff sk_buff-> user [skip csum]
Alan> While it seems a really dumb thing to do it makes sense as Alan> there may be retransmissions and thus the receiver cannot go Alan> using the queue pointers of the senders buffer copy. Its a Alan> bad case solely applicable to loopback, and if we are going Alan> to optimise loopback tcp we should do the solaris trick and Alan> dump everything. In the mean time thats what AF_UNIX was Alan> invented for.
me> On the TCP i've been seting up for 2.1 there is no need for me> copy number 2 since the skb is cloned (the copy is restricted me> to the skb header).
Well, i've been looking at the code and loopback does a clone of the skb (the right thing to do) so there are really 2 data copies only. There is the memcpy of the skb header but that does not seam to show on Linus profile trace (it's 30-40 bytes for each 3k).
regards, ./Pedro.
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