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SubjectRe: Fix for SLOW PPP Bug
I do think that there is an improvement in the telnet interactive stuff 
using the enclosed patch. My modem was never snappy before the problems
occured but now it is nolonger dreadfully slow and clunky.

tim...


--
Tim Middelkoop O
http://intrism.hcsys.com/~mtim /\,
mtim@freenet.tlh.fl.us \/\
----Try linux today---- /

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O M V-- PS+ PE Y+ PGP t 5 X R- tv b++ DI? D+ G e+ h-- r-- y+


On Wed, 10 Apr 1996, Linus Torvalds wrote:

> Umm.. I've been looking at the use of "tcp_reset_xmit_timer()", and it may be
> that we're seeing a timer fight between the delayed acks and retransmissions,
> where both want to use the same timer and they don't like each other messing
> with it..
>
> Anyway, this would indeed have gotten worse in 1.3.73, because that started
> using more of the delayed ack logic (the code isn't new per se, it's just used
> in a new way). That could have made the problem much worse.
>
> Anyway, one way to test out this theory would be to check out "tcp_queue()" in
> tcp_input.c, and find the place where it does something like this:
>
> if (!sk->delay_acks || th->fin) {
> tcp_send_ack(...
> }
> else
> {
> ...
>
> Now, what happens if you change the test to use the "tcp_send_ack()" path a lot
> more, and not use the "else" path as much (the else path does the delayed ack
> thing, and if it is messed up the retransmission code..)
>
> I'd suggest changing the "if" case to something like this:
>
> if (!sk->delay_acks || th->fin ||
> sk->bytes_rcv > sk->max_unacked ||
> sk->ato > HZ/2 ||
> tcp_raise_window(sk)) {
> tcp_send_ack(...
> }
> else
> {
>
> (That is essentially what 1.3.72 uses, and while I don't particularly like the
> extra cases it might help to be overly cautious in this case..)
>
> If you do test this, please remove any other patches to your system (ie try the
> above on a clean 1.3.84 or 85 kernel), so that I don't need to worry about lots
> of different patches..
>
> Linus
>


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