Latency spikes on FreeBSD 8.2 with kernel scan function.

[Pawel Tyll]

>> I do have dummynet configured, but like I said - every 20 seconds
>> network freezes for about 0.5s. Guess what happens every 20 seconds...
>> You got it! Protocol "kernel" scans the kernel routes. Also, after
>> /usr/local/etc/rc.d/bird stop, problem is gone. What could be causing
> bird is stopped, traffic forwarding is stopped (since dynamic routes
> disappers) ?
> Perhaps your configuration shapes ALL (e.g. network AND local) traffic
> withing single queue? If so, when queue is full with network traffic
> even local traffic is delayed ?
No  no.  And  there's  almost  no traffic. There's one IBGP peer, this
machine  isn't  in  production yet. It was for a moment, but had to be
pulled because of this. I'm 100% certain this has something to do with
'scan' facility of 'kernel' protocol.

ping -M time -i 0.01 127.0.0.1:

76 bytes from 127.0.0.1: icmp_seq=3207 ttl=64 time=0.015 ms tso=08:40:08 tsr=08:40:08 tst=08:40:08
76 bytes from 127.0.0.1: icmp_seq=3208 ttl=64 time=0.016 ms tso=08:40:08 tsr=08:40:08 tst=08:40:08
76 bytes from 127.0.0.1: icmp_seq=3209 ttl=64 time=149.246 ms tso=08:40:08 tsr=08:40:08 tst=08:40:08
76 bytes from 127.0.0.1: icmp_seq=3210 ttl=64 time=169.547 ms tso=08:40:08 tsr=08:40:08 tst=08:40:08
76 bytes from 127.0.0.1: icmp_seq=3211 ttl=64 time=0.028 ms tso=08:40:08 tsr=08:40:08 tst=08:40:08
76 bytes from 127.0.0.1: icmp_seq=3212 ttl=64 time=0.022 ms tso=08:40:08 tsr=08:40:08 tst=08:40:08

76 bytes from 127.0.0.1: icmp_seq=4948 ttl=64 time=0.017 ms tso=08:40:27 tsr=08:40:27 tst=08:40:27
76 bytes from 127.0.0.1: icmp_seq=4949 ttl=64 time=0.016 ms tso=08:40:27 tsr=08:40:27 tst=08:40:27
76 bytes from 127.0.0.1: icmp_seq=4950 ttl=64 time=150.495 ms tso=08:40:27 tsr=08:40:28 tst=08:40:28
76 bytes from 127.0.0.1: icmp_seq=4951 ttl=64 time=0.026 ms tso=08:40:28 tsr=08:40:28 tst=08:40:28
76 bytes from 127.0.0.1: icmp_seq=4952 ttl=64 time=0.026 ms tso=08:40:28 tsr=08:40:28 tst=08:40:28

76 bytes from 127.0.0.1: icmp_seq=8586 ttl=64 time=0.016 ms tso=08:41:08 tsr=08:41:08 tst=08:41:08
76 bytes from 127.0.0.1: icmp_seq=8587 ttl=64 time=0.016 ms tso=08:41:08 tsr=08:41:08 tst=08:41:08
76 bytes from 127.0.0.1: icmp_seq=8588 ttl=64 time=149.361 ms tso=08:41:08 tsr=08:41:08 tst=08:41:08
76 bytes from 127.0.0.1: icmp_seq=8589 ttl=64 time=168.944 ms tso=08:41:08 tsr=08:41:08 tst=08:41:08
76 bytes from 127.0.0.1: icmp_seq=8590 ttl=64 time=0.026 ms tso=08:41:08 tsr=08:41:08 tst=08:41:08
76 bytes from 127.0.0.1: icmp_seq=8591 ttl=64 time=0.021 ms tso=08:41:08 tsr=08:41:08 tst=08:41:08

Nov 22 09:40:08 storm bird: kernel1: Scanning routing table
Nov 22 09:40:08 storm bird: kernel1: Pruning table master
Nov 22 09:40:27 storm bird: kernel1: Scanning routing table
Nov 22 09:40:28 storm bird: kernel1: Pruning table master
Nov 22 09:40:47 storm bird: kernel1: Scanning routing table
Nov 22 09:40:48 storm bird: kernel1: Pruning table master
Nov 22 09:41:08 storm bird: kernel1: Scanning routing table
Nov 22 09:41:09 storm bird: kernel1: Pruning table master

bird> show protocols
name     proto    table    state  since       info
kernel1  Kernel   master   up     02:52
device1  Device   master   up     02:52
NN_Gate  BGP      master   up     02:52       Established
static1  Static   master   down   09:36