I've installed Martin's patch and set min_turn_time to 10000
(10ms).

It's certainly made a difference. Ping round trip times have
dropped by about a second, but I'm afraid we're still not quite
there: GPRS download bandwidth is up from 1.0KB/s to 1.3KB/s, but
still not the 3.6KB/s I get with an old fashioned RS232 cable.

One slightly intriguing and possibly relevant thing is ping's
output. Normally, GPRS ping times are all over the shop, from
700ms to 1500ms. Without Martin's patch, the ping times including
the IrDA link were about 1000ms longer. With the patch, the
values seem to get highly quantized:

/tmp > ping gauntlet
PING gauntlet.cl.cam.ac.uk (10.10.8.69) from 10.10.99.14 : 56(84) bytes of data.
64 bytes from gauntlet.cl.cam.ac.uk (10.10.8.69): icmp_seq=0 ttl=248 time=1.539 sec
64 bytes from gauntlet.cl.cam.ac.uk (10.10.8.69): icmp_seq=1 ttl=248 time=1.030 sec
64 bytes from gauntlet.cl.cam.ac.uk (10.10.8.69): icmp_seq=2 ttl=248 time=1.030 sec
64 bytes from gauntlet.cl.cam.ac.uk (10.10.8.69): icmp_seq=3 ttl=248 time=1.030 sec
64 bytes from gauntlet.cl.cam.ac.uk (10.10.8.69): icmp_seq=4 ttl=248 time=1.542 sec
64 bytes from gauntlet.cl.cam.ac.uk (10.10.8.69): icmp_seq=5 ttl=248 time=1.551 sec
64 bytes from gauntlet.cl.cam.ac.uk (10.10.8.69): icmp_seq=6 ttl=248 time=1.030 sec
64 bytes from gauntlet.cl.cam.ac.uk (10.10.8.69): icmp_seq=7 ttl=248 time=1.029 sec
64 bytes from gauntlet.cl.cam.ac.uk (10.10.8.69): icmp_seq=8 ttl=248 time=1.029 sec
64 bytes from gauntlet.cl.cam.ac.uk (10.10.8.69): icmp_seq=9 ttl=248 time=1.030 sec
64 bytes from gauntlet.cl.cam.ac.uk (10.10.8.69): icmp_seq=10 ttl=248 time=1.030 sec
64 bytes from gauntlet.cl.cam.ac.uk (10.10.8.69): icmp_seq=11 ttl=248 time=1.030 sec


I've recorded another irdadump trace of downloading a file via
HTTP over GPRS. As you can see, there's still several ~500ms
timeouts.

Grateful for any pointers!

Thanks,
Ian

------

> cat /proc/sys/net/irda/min_tx_turn_time 
10000

17:55:16.186822 (0032.51 ms) i:rsp  < ca=22 pf=0 nr=2 ns=3 LM slsap=02 dlsap=16 (206) 
17:55:16.206194 (0019.37 ms) i:rsp  < ca=22 pf=0 nr=2 ns=4 LM slsap=02 dlsap=16 (206) 
17:55:16.225537 (0019.34 ms) i:rsp  < ca=22 pf=1 nr=2 ns=5 LM slsap=02 dlsap=16 (206) 
17:55:16.225728 (0000.19 ms) i:cmd  > ca=22 pf=1 nr=6 ns=2 LM slsap=16 dlsap=02 (82) 
17:55:16.265609 (0039.88 ms) i:rsp  < ca=22 pf=0 nr=3 ns=6 LM slsap=02 dlsap=16 (206) 
17:55:16.285781 (0020.17 ms) i:rsp  < ca=22 pf=0 nr=3 ns=7 LM slsap=02 dlsap=16 (206) 
17:55:16.305315 (0019.53 ms) i:rsp  < ca=22 pf=1 nr=3 ns=0 LM slsap=02 dlsap=16 (206) 
17:55:16.804316 (0499.00 ms) rr:cmd > ca=22 pf=1 nr=1 (2) 
17:55:16.836231 (0031.92 ms) i:rsp  < ca=22 pf=0 nr=3 ns=1 LM slsap=02 dlsap=16 (206) 
17:55:16.855684 (0019.45 ms) i:rsp  < ca=22 pf=0 nr=3 ns=2 LM slsap=02 dlsap=16 (206) 
17:55:16.875205 (0019.52 ms) i:rsp  < ca=22 pf=1 nr=3 ns=3 LM slsap=02 dlsap=16 (206) 
17:55:17.374321 (0499.12 ms) rr:cmd > ca=22 pf=1 nr=4 (2) 
17:55:17.406416 (0032.10 ms) i:rsp  < ca=22 pf=0 nr=3 ns=4 LM slsap=02 dlsap=16 (206) 
17:55:17.426053 (0019.64 ms) i:rsp  < ca=22 pf=0 nr=3 ns=5 LM slsap=02 dlsap=16 (206) 
17:55:17.445476 (0019.42 ms) i:rsp  < ca=22 pf=1 nr=3 ns=6 LM slsap=02 dlsap=16 (206) 
17:55:17.445536 (0000.06 ms) i:cmd  > ca=22 pf=1 nr=7 ns=3 LM slsap=16 dlsap=02 (91) 
17:55:17.485664 (0040.13 ms) i:rsp  < ca=22 pf=0 nr=4 ns=7 LM slsap=02 dlsap=16 (206) 
17:55:17.505388 (0019.72 ms) i:rsp  < ca=22 pf=0 nr=4 ns=0 LM slsap=02 dlsap=16 (206) 
17:55:17.525112 (0019.72 ms) i:rsp  < ca=22 pf=1 nr=4 ns=1 LM slsap=02 dlsap=16 (206) 
17:55:18.024330 (0499.22 ms) rr:cmd > ca=22 pf=1 nr=2 (2) 
17:55:18.056237 (0031.91 ms) i:rsp  < ca=22 pf=0 nr=4 ns=2 LM slsap=02 dlsap=16 (206) 
17:55:18.076039 (0019.80 ms) i:rsp  < ca=22 pf=0 nr=4 ns=3 LM slsap=02 dlsap=16 (206) 
17:55:18.095375 (0019.34 ms) i:rsp  < ca=22 pf=1 nr=4 ns=4 LM slsap=02 dlsap=16 (206) 
17:55:18.095567 (0000.19 ms) i:cmd  > ca=22 pf=1 nr=5 ns=4 LM slsap=16 dlsap=02 (90) 
17:55:18.135509 (0039.94 ms) i:rsp  < ca=22 pf=0 nr=5 ns=5 LM slsap=02 dlsap=16 (206) 
17:55:18.155060 (0019.55 ms) i:rsp  < ca=22 pf=0 nr=5 ns=6 LM slsap=02 dlsap=16 (206) 
17:55:18.174306 (0019.25 ms) i:rsp  < ca=22 pf=1 nr=5 ns=7 LM slsap=02 dlsap=16 (206) 
17:55:18.674347 (0500.04 ms) rr:cmd > ca=22 pf=1 nr=0 (2) 
17:55:18.707444 (0033.10 ms) i:rsp  < ca=22 pf=0 nr=5 ns=0 LM slsap=02 dlsap=16 (206) 
17:55:18.727149 (0019.70 ms) i:rsp  < ca=22 pf=0 nr=5 ns=1 LM slsap=02 dlsap=16 (206) 
17:55:18.747047 (0019.90 ms) i:rsp  < ca=22 pf=1 nr=5 ns=2 LM slsap=02 dlsap=16 (206) 
17:55:19.244346 (0497.30 ms) rr:cmd > ca=22 pf=1 nr=3 (2) 
17:55:19.276919 (0032.57 ms) i:rsp  < ca=22 pf=0 nr=5 ns=3 LM slsap=02 dlsap=16 (206) 
17:55:19.296314 (0019.40 ms) i:rsp  < ca=22 pf=0 nr=5 ns=4 LM slsap=02 dlsap=16 (206) 
17:55:19.315997 (0019.68 ms) i:rsp  < ca=22 pf=1 nr=5 ns=5 LM slsap=02 dlsap=16 (206) 
17:55:19.316058 (0000.06 ms) i:cmd  > ca=22 pf=1 nr=6 ns=5 LM slsap=16 dlsap=02 (83) 
17:55:19.355965 (0039.91 ms) i:rsp  < ca=22 pf=0 nr=6 ns=6 LM slsap=02 dlsap=16 (206) 
17:55:19.375990 (0020.02 ms) i:rsp  < ca=22 pf=0 nr=6 ns=7 LM slsap=02 dlsap=16 (206) 
17:55:19.396326 (0020.34 ms) i:rsp  < ca=22 pf=1 nr=6 ns=0 LM slsap=02 dlsap=16 (206) 
17:55:19.894356 (0498.03 ms) rr:cmd > ca=22 pf=1 nr=1 (2) 
17:55:19.926788 (0032.43 ms) i:rsp  < ca=22 pf=0 nr=6 ns=1 LM slsap=02 dlsap=16 (206) 
17:55:19.946235 (0019.45 ms) i:rsp  < ca=22 pf=0 nr=6 ns=2 LM slsap=02 dlsap=16 (206) 
17:55:19.965661 (0019.43 ms) i:rsp  < ca=22 pf=1 nr=6 ns=3 LM slsap=02 dlsap=16 (206) 
17:55:19.965729 (0000.07 ms) i:cmd  > ca=22 pf=1 nr=4 ns=6 LM slsap=16 dlsap=02 (82) 
17:55:20.005345 (0039.62 ms) i:rsp  < ca=22 pf=0 nr=7 ns=4 LM slsap=02 dlsap=16 (206) 
17:55:20.025388 (0020.04 ms) i:rsp  < ca=22 pf=0 nr=7 ns=5 LM slsap=02 dlsap=16 (206) 
17:55:20.045013 (0019.62 ms) i:rsp  < ca=22 pf=1 nr=7 ns=6 LM slsap=02 dlsap=16 (206) 
17:55:20.544362 (0499.35 ms) rr:cmd > ca=22 pf=1 nr=7 (2) 
17:55:20.576453 (0032.09 ms) i:rsp  < ca=22 pf=0 nr=7 ns=7 LM slsap=02 dlsap=16 (206) 
17:55:20.595990 (0019.54 ms) i:rsp  < ca=22 pf=0 nr=7 ns=0 LM slsap=02 dlsap=16 (206) 
17:55:20.615418 (0019.43 ms) i:rsp  < ca=22 pf=1 nr=7 ns=1 LM slsap=02 dlsap=16 (206) 
17:55:21.114370 (0498.95 ms) rr:cmd > ca=22 pf=1 nr=2 (2) 
17:55:21.146376 (0032.01 ms) i:rsp  < ca=22 pf=0 nr=7 ns=2 LM slsap=02 dlsap=16 (206) 
17:55:21.165566 (0019.19 ms) i:rsp  < ca=22 pf=0 nr=7 ns=3 LM slsap=02 dlsap=16 (206) 
17:55:21.184737 (0019.17 ms) i:rsp  < ca=22 pf=1 nr=7 ns=4 LM slsap=02 dlsap=16 (206) 
17:55:21.184796 (0000.06 ms) i:cmd  > ca=22 pf=1 nr=5 ns=7 LM slsap=16 dlsap=02 (83) 
17:55:21.224332 (0039.54 ms) i:rsp  < ca=22 pf=0 nr=0 ns=5 LM slsap=02 dlsap=16 (206) 
17:55:21.244299 (0019.97 ms) i:rsp  < ca=22 pf=0 nr=0 ns=6 LM slsap=02 dlsap=16 (206) 
17:55:21.263970 (0019.67 ms) i:rsp  < ca=22 pf=1 nr=0 ns=7 LM slsap=02 dlsap=16 (206) 
17:55:21.754378 (0490.41 ms) rr:cmd > ca=22 pf=1 nr=0 (2) 
17:55:21.786572 (0032.19 ms) i:rsp  < ca=22 pf=0 nr=0 ns=0 LM slsap=02 dlsap=16 (206) 
17:55:21.805836 (0019.26 ms) i:rsp  < ca=22 pf=0 nr=0 ns=1 LM slsap=02 dlsap=16 (206) 
17:55:21.825356 (0019.52 ms) i:rsp  < ca=22 pf=1 nr=0 ns=2 LM slsap=02 dlsap=16 (206) 
17:55:21.825429 (0000.07 ms) i:cmd  > ca=22 pf=1 nr=3 ns=0 LM slsap=16 dlsap=02 (74) 
17:55:21.864217 (0038.79 ms) i:rsp  < ca=22 pf=0 nr=1 ns=3 LM slsap=02 dlsap=16 (206) 
17:55:21.883495 (0019.28 ms) i:rsp  < ca=22 pf=0 nr=1 ns=4 LM slsap=02 dlsap=16 (206) 
17:55:21.902847 (0019.35 ms) i:rsp  < ca=22 pf=1 nr=1 ns=5 LM slsap=02 dlsap=16 (206) 
17:55:22.394387 (0491.54 ms) rr:cmd > ca=22 pf=1 nr=6 (2) 
17:55:22.427009 (0032.62 ms) i:rsp  < ca=22 pf=0 nr=1 ns=6 LM slsap=02 dlsap=16 (206) 
17:55:22.446740 (0019.73 ms) i:rsp  < ca=22 pf=0 nr=1 ns=7 LM slsap=02 dlsap=16 (206) 
17:55:22.461447 (0014.71 ms) i:rsp  < ca=22 pf=1 nr=1 ns=0 LM slsap=02 dlsap=16 (146) 
17:55:22.461648 (0000.20 ms) i:cmd  > ca=22 pf=1 nr=1 ns=1 LM slsap=16 dlsap=02 (74) 
17:55:22.488601 (0026.95 ms) rr:rsp < ca=22 pf=1 nr=2 (2) 
17:55:22.984392 (0495.79 ms) rr:cmd > ca=22 pf=1 nr=1 (2) 
17:55:23.007910 (0023.52 ms) rr:rsp < ca=22 pf=1 nr=2 (2) 
17:55:23.504398 (0496.49 ms) rr:cmd > ca=22 pf=1 nr=1 (2) 
17:55:23.536621 (0032.22 ms) i:rsp  < ca=22 pf=0 nr=2 ns=1 LM slsap=02 dlsap=16 (206) 
17:55:23.555897 (0019.28 ms) i:rsp  < ca=22 pf=0 nr=2 ns=2 LM slsap=02 dlsap=16 (206) 
17:55:23.575620 (0019.72 ms) i:rsp  < ca=22 pf=1 nr=2 ns=3 LM slsap=02 dlsap=16 (206) 
17:55:24.074405 (0498.79 ms) rr:cmd > ca=22 pf=1 nr=4 (2) 
17:55:24.106916 (0032.51 ms) i:rsp  < ca=22 pf=0 nr=2 ns=4 LM slsap=02 dlsap=16 (206) 
17:55:24.126715 (0019.80 ms) i:rsp  < ca=22 pf=0 nr=2 ns=5 LM slsap=02 dlsap=16 (206) 
17:55:24.146164 (0019.45 ms) i:rsp  < ca=22 pf=1 nr=2 ns=6 LM slsap=02 dlsap=16 (206) 
17:55:24.644416 (0498.25 ms) rr:cmd > ca=22 pf=1 nr=7 (2) 
17:55:24.676423 (0032.01 ms) i:rsp  < ca=22 pf=0 nr=2 ns=7 LM slsap=02 dlsap=16 (206) 
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