On Tue, 2008-10-07 at 13:24 -0400, bill wrote: > > Kieran Mansley wrote: > > >> Thank you for any feedback on this. > > >> > > > > > > I don't know of any timers that have that periodicity in lwIP. > > None. > > > It might > > > be useful to get a packet capture from just before the poor performance > > > that we could look at in ethereal - that might give a clue about why the > > > performance is poor. > > > > > The first thing I would do is to check whether this is a real delay in > > your device or a simple TCP retransmission delay (i.e. the first > > response has a bad checksum or something like that and the PC has to > > wait for the device to retransmit). > > I strongly suspect the latter. > > Thanks to both of you. I wanted to add to lwIP_stats when retransmissions > occur so I know if something was missed or there are errors. I had trouble > finding where all of the error recovery retransmissions occur. > > Is putting debug traces in tcp_rexmit_rto sufficient to catch when they > occur?
No, that will only get retransmissions after a timeout, not the fast retransmissions after duplicate ACKs. You also need to trace tcp_rexmit () > One point is truly interesting. I can send 10MB/S (1MB every 100mS) for > ~9.5 minutes, or sit for 9 minutes while sending the 836 byte "I'm here" > packet once per second and then start the 1MB/100mS transfers and at ~9:30 > it fails. There have been a few times that I've seen a program crash or > memory corruption but most often the drop in bandwidth is what starts things > off, and it is repeatable (from 9:25 to 9:40). The time seems to start then > the connection is made. It doesn't matter how long the firmware is running > before the connection takes place. The connection can be terminated from > the PC and reconnected and it still times out at 9:30 or so from the first > connection. It makes it seem like an uninitialized variable in the > connection management. That truly is weird. If you can get a packet capture from just before the failure, I'd be happy to take a look. Thanks Kieran _______________________________________________ lwip-users mailing list [email protected] http://lists.nongnu.org/mailman/listinfo/lwip-users
