Date: Thu, 25 Mar 2010 15:22:04 +0100 From: Attila Nagy <bra@fsn.hu> To: Mailing List FreeBSD Stable <freebsd-stable@FreeBSD.org> Subject: 8-STABLE freezes on UDP traffic (DNS), 7.x doesn't Message-ID: <4BAB718C.3090001@fsn.hu>
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Hi, 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 interfaces). 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 normal. 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. top says: last pid: 92428; load averages: 0.49, 0.40, 0.38 up 0+21:13:18 07:41:43 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 Swap: 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% python2.6 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% python2.6 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% readproctit 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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