usmsc weirdness (was: How to install the new kernel image?)

[Tom Ivar Helbekkmo <tih%hamartun.priv.no@localhost>]

I can't really experiment any more with my Pi until the next time I'm at
the cabin -- partly because I really need it to keep working until then,
so I can use it to turn on the heat up there before I go...  :)

However, in addition to the hang at usmsc0 ifconfig time if there's
little or nothing else connected to USB, there's another interesting
thing that keeps happening to that ethernet interface: after it's been
up for a while (like a couple days or so, it seems), it'll start
processing packets in bursts.

I notice that it's begun because interactive command line use on the Pi
from home becomes bursty.  If I press and hold a key, I'll get about
thirty characters echoed at a time, with a little over a second between
each burst.  This goes through an OpenVPN tunnel, though, so that'll
color things a bit.  However, if I start a ping up there, targetting
something that the Pi won't go through the OpenVPN tunnel for, I get:

: otium# ;ping 8.8.8.8
PING google-public-dns-a.google.com (8.8.8.8): 56 data bytes
64 bytes from 8.8.8.8: icmp_seq=0 ttl=45 time=41.486840 ms
64 bytes from 8.8.8.8: icmp_seq=1 ttl=45 time=411.642487 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=45 time=875.221521 ms
64 bytes from 8.8.8.8: icmp_seq=3 ttl=45 time=1200.636420 ms
64 bytes from 8.8.8.8: icmp_seq=4 ttl=45 time=191.866634 ms
64 bytes from 8.8.8.8: icmp_seq=5 ttl=45 time=586.544595 ms
64 bytes from 8.8.8.8: icmp_seq=6 ttl=45 time=975.001732 ms
64 bytes from 8.8.8.8: icmp_seq=7 ttl=45 time=42.104822 ms
64 bytes from 8.8.8.8: icmp_seq=8 ttl=45 time=361.492890 ms
64 bytes from 8.8.8.8: icmp_seq=9 ttl=45 time=751.021995 ms
64 bytes from 8.8.8.8: icmp_seq=10 ttl=45 time=1141.553075 ms
64 bytes from 8.8.8.8: icmp_seq=11 ttl=45 time=142.675010 ms
64 bytes from 8.8.8.8: icmp_seq=12 ttl=45 time=527.349251 ms
64 bytes from 8.8.8.8: icmp_seq=13 ttl=45 time=927.257068 ms
64 bytes from 8.8.8.8: icmp_seq=14 ttl=45 time=42.123822 ms
64 bytes from 8.8.8.8: icmp_seq=15 ttl=45 time=315.475177 ms
64 bytes from 8.8.8.8: icmp_seq=16 ttl=45 time=701.620378 ms
64 bytes from 8.8.8.8: icmp_seq=17 ttl=45 time=1089.700526 ms
64 bytes from 8.8.8.8: icmp_seq=18 ttl=45 time=91.295447 ms
64 bytes from 8.8.8.8: icmp_seq=19 ttl=45 time=477.112657 ms
64 bytes from 8.8.8.8: icmp_seq=20 ttl=45 time=878.147443 ms
64 bytes from 8.8.8.8: icmp_seq=21 ttl=45 time=1225.706725 ms
64 bytes from 8.8.8.8: icmp_seq=22 ttl=45 time=255.099866 ms
64 bytes from 8.8.8.8: icmp_seq=23 ttl=45 time=655.797662 ms
64 bytes from 8.8.8.8: icmp_seq=24 ttl=45 time=1042.638845 ms
64 bytes from 8.8.8.8: icmp_seq=25 ttl=45 time=44.070767 ms
^C64 bytes from 8.8.8.8: icmp_seq=26 ttl=45 time=429.284996 ms

----google-public-dns-a.google.com PING Statistics----
27 packets transmitted, 27 packets received, 0.0% packet loss
round-trip min/avg/max/stddev =
41.486840/571.256617/1225.706725/397.879518 ms
: otium# ;

Note how it varies between reasonable RTTs and "a little over a second",
which is the time between bursts over the VPN tunnel.

This keeps happening with the Pi, but I've never observed anything like
this with my NetBSD-amd64 laptop while I've been up there with it, and I
have had that running up there for many days at a time.

-tih
-- 
Most people who graduate with CS degrees don't understand the significance
of Lisp.  Lisp is the most important idea in computer science.  --Alan Kay