8-STABLE freezes on UDP traffic (DNS), 7.x doesn't
bra at fsn.hu
Thu Mar 25 14:41:28 UTC 2010
I have some recursive nameservers, running unbound and 7.2-STABLE #0:
Wed Sep 2 13:37:17 CEST 2009 on a bunch of HP BL460c machines (bce
These work OK.
During the process of migrating to 8.x, I've upgraded one of these
machines to 8.0-STABLE #25: Tue Mar 9 18:15:34 CET 2010 (the dates
indicate an approximate time, when the source was checked out from
cvsup.hu.freebsd.org, I don't know the exact revision).
The first problem was that the machine occasionally lost network access
for some minutes. I could log in on the console, and I could see the
processes, involved in network IO in "keglim" state, but couldn't do any
network IO. This lasted for some minutes, then everything came back to
I could fix this issue by raising kern.ipc.nmbclusters to 51200
(doubling from its default size), when I can't see these blackouts.
But now the machine freezes. It can run for about a day, and then it
just freezes. I can't even break in to the debugger with sending NMI to it.
last pid: 92428; load averages: 0.49, 0.40, 0.38 up 0+21:13:18
43 processes: 2 running, 38 sleeping, 1 zombie, 2 lock
CPU: 1.3% user, 0.0% nice, 1.3% system, 26.0% interrupt, 71.3% idle
Mem: 1682M Active, 99M Inact, 227M Wired, 5444K Cache, 44M Buf, 5899M Free
PID USERNAME THR PRI NICE SIZE RES STATE C TIME WCPU COMMAND
45011 bind 4 49 0 1734M 1722M RUN 2 37:42 22.17% unbound
712 bind 3 44 0 70892K 19904K uwait 0 71:07 3.86%
The common in these freezes seems to be the high interrupt count.
Normally, during load the CPU times look like this:
CPU: 3.5% user, 0.0% nice, 1.8% system, 0.4% interrupt, 94.4% idle
I could observe a "freeze", where top remained running and everything
was 0%, except interrupt, which was 25% exactly (the machine has four
cores), and another, where I could save the following console output:
CPU: 0.0% user, 0.0% nice, 0.2% system, 50.0% interrupt, 49.8% idle
.......(partial, broken line)....32M 2423M *udp 1 50:16 10.89% unbound
714 bind 3 44 0 70892K 26852K uwait 3 8:41 4.69%
61004 root 1 62 0 37428K 10876K *udp 1 0:00 1.56% python
706 root 1 44 0 2696K 624K piperd 1 0:07 0.00%
Both unbound and python accepts DNS requests, and it seems when 25%
interrupt happens, only unbound is in *udp state, where it is 50%, both
programs are in that state.
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