Messages in this thread |  | | Date | Sun, 9 Jun 1996 00:23:07 +0100 | From | Pedro Roque Marques <> | Subject | Re: Speed of memcpy, csum_partial and csum_partial_copy |
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>>>>> "Alan" == Alan Cox <alan@lxorguk.ukuu.org.uk> writes:
>> In short, the two copies that occur in TCP loopback (first from >> the sender into the kernel, and then from the kernel into the >> receiver) alone account for 60% of the TCP stack..
Alan> There are three for TCP loopback unless someone has fiddled Alan> recently. We copy
user-> sk_buff [with csum] Alan> 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.
On the TCP i've been seting up for 2.1 there is no need for copy number 2 since the skb is cloned (the copy is restricted to the skb header).
Well, gonna try removing that copy you mention to see if it increases performance. Is it done on the loopback device itself ?
regards, Pedro.
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