LDB wrote:
kalash nainwal wrote:
On 2/22/07, kristrev@xxxxxxxxxxxxxxxxxxxxx
<kristrev@xxxxxxxxxxxxxxxxxxxxx> wrote:
Hello,
I am working on optimizing the TCP-code for a certain type of TCP-stream,
and to make one of my optimizations work I need to copy data from one SKB
(the data field of the skb) to another SKB (data field).
Currently I am using memcpy, and it does what it is supposed to, but I am
curious as to if there are any other (potentially faster/more efficient)
ways of doing it. I have checked out the skb_add_data (used when you can
copy data from the msg you are sending into the most recent skb added to
the queue), but from what I can understand it only copies from userspace
into kernelspace (whereas I need to copy kernel-kernel).
Does anyone have any hints, suggestions, solutions or something else they
think might help?
Thanks,
Kristian
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How about cloning? Is that an option?
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skb_clone is an option but you cannot modify any data - correct me if I am wrong.
The other options are pskb_copy and skb_copy used when modifications are
necessary - correct if I am wrong.
You just have to chose which is appropriate for your specific needs.
LDB
Thank you very much for all your replies. I have spent the day today
looking into the different clone/copy-functions for skb's, but I cant
help feeling that they are a bit to advanced for what I want to do. All
my code is going to do is to copy the skb->data field (the payload) from
one skb to another (to perform some aggressive bundling, the potentially
redundant data will be removed when ack occurs).
Since the data copied might be from the retransmission queue, the
function I see might be useful is the skb_copy function to copy the
packet that I copy the data from (if it is in the retransmission queue).
This is also what led to my question about exactly how TCP treats
acks/sends on the same socket.
My current implementation (using memcopy) copies the data, but some
weird behaviour occurs (and after days of looking into it I havent found
the cause). If a dupAck occurs, it rightly sends as many packets from
the retrans-queue as it is supposed to (and allowed to) do but then
eveything stops working. Even though the sequence number is correct, I
only recieves more dupAcks. If someone has experienced similar behaviour
when working with the TCP-code or have any ideas to what might be wrong,
please let me know :)
Have a nice weekend!
Thanks,
Kristian
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