Here's a strange one.  DGN3500 running trunk 49276 but this is an issue that's been around for a while (year+) so I don't think it's directly 'trunk' related.

System uses ADSL with PPPoA - long line so sync is around 2.5mbit incoming, 0.5mbit outgoing.  Traffic to/from Internet via lan/wlan achieves those rates no problem.  Traffic from internet to process running on router achieves 2.5mbit incoming rate no problem.  Traffic TO internet from process running on router seems to be rate limited to about a tenth of the outbound sync rate ie. 40kbps when it should be more 400kbps.

This is evidenced with 'netperf/netserver', also 'scp' and 'ssh' sessions are extremely laggy.  The Luci web interface also understandably suffers. 

As previously mentioned, external devices (e.g. ipad/PC) can do speedtests and acheive 'line rates' in both directions, so why/what could be causing router processes only to be unable to send data quickly?

time dmesg >/dev/null
real    0m 0.07s
user    0m 0.03s
sys     0m 0.01s

time dmesg >/tmp/zzz
real    0m 0.05s
user    0m 0.02s
sys     0m 0.02s

time dmesg >/mnt/sda2/zzz
real    0m 0.06s
user    0m 0.03s
sys     0m 0.02s

dmesg
real    0m 39.86s!!!!
user    0m 0.04s
sys     0m 0.03s

I stuck wireshark on the receiving end and saw no retries/lost packets or anything other than to suggest a slow link....but it isn't *that* slow!

I'd be really grateful for any ideas/pointers.