Em Fri, Jan 04, 2008 at 11:25:29AM +1300, Ian McDonald escreveu:
On Jan 4, 2008 11:19 AM, Tomasz Grobelny [EMAIL PROTECTED] wrote:
I think I almost got it. Thanks a lot for the detailed explanation. But I've
got two more questions:
1. How can I control the amount of memory allowed to be allocated for the
socket send buffer? It it somehow connected with tx_qlen or is it not?
I wrote the code here so let me comment - there is no fixed amount of
memory allocated - it is determined by the tx_qlen. I was looking at
there is no memory allocated in advance nor explicit, DCCP specific
mechanism for limiting the amount of memory a socket can use for its
write queue, but DCCP uses sock_alloc_send_skb and that function does
memory accounting and checks if the maximum memory (SO_SNDBUF) has been
reached, when it makes the app to sleep if O_NONBLOCK is not set.
implementing memory limits but it got too hard and as DCCP doesn't
combine packets I thought it made it much simpler just to put a limit
by packets.
2. If I decide that for whatever reason a given skb already in
sk_write_queue
should not be transmitted I should remove it from queue and call kfree_skb
on
it, it that right?
Correct. Remember of course all your locking mechanisms. If you want a
good example look at the below towards the end:
http://wand.net.nz/~iam4/dccp/patches20/30-best_packet_next.diff
(NB this patch applies against 2.6.20 after previous patches in series).
Correct if he is in-kernel.
- Arnaldo
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