On Tue, May 15, 2012 at 03:02:37PM +0100, Brian Candler wrote:
> Update:
>
> After a week away, I am continuing to try to narrow down the problem of this
> system withing hanging I/O.
>
> I can fairly reliably repeat the problem on a system with 24 disks, and I've
> embarked on trying some different configs to see what's the simplest way I
> can make this die.
>
> During this, I found something of interest: I happened to leave an 'iostat
> 5' process running, and that hung too. i.e. ps showed it in 'D+' state, and
> it was unkillable.
>
> root 34 0.6 0.0 0 0 ? D 11:29 1:18 [kswapd0]
> root 1258 0.0 0.0 15976 532 ? Ds 11:29 0:00 /usr/sbin/irqbalance
> root 1421 0.0 0.0 0 0 ? D 12:49 0:01 [xfsaild/md127]
> snmp 1430 0.0 0.0 48608 3440 ? D 11:29 0:00 /usr/sbin/snmpd -Lsd -Lf /dev/null -u snmp -g snmp -I -smux -p /var/run/snmpd.pid
> xxxx 1614 1.1 0.0 378860 3812 pts/1 D+ 12:50 1:15 bonnie++ -d /disk/scratch/test -s 16384k -n 98:800k:500k:1000
> xxxx 1669 1.2 0.0 378860 3816 pts/2 D+ 12:50 1:21 bonnie++ -d /disk/scratch/test -s 16384k -n 98:800k:500k:1000
> xxxx 1727 0.5 0.0 383424 692 pts/3 Dl+ 12:51 0:37 bonnie++ -d /disk/scratch/test -s 16384k -n 98:800k:500k:1000
> xxxx 1782 1.2 0.0 378860 3824 pts/4 D+ 12:51 1:20 bonnie++ -d /disk/scratch/test -s 16384k -n 98:800k:500k:1000
> xxxx 1954 0.0 0.0 5912 544 pts/0 D+ 12:58 0:00 iostat 5
> root 2642 0.2 0.0 0 0 ? D 13:25 0:09 [kworker/0:1]
> root 3233 0.0 0.0 5044 168 ? Ds 13:50 0:00 /usr/sbin/sshd -D -R
> xxxx 4648 0.0 0.0 8104 936 pts/6 S+ 14:41 0:00 grep --color=auto D
> root 29491 0.0 0.0 0 0 ? D 12:45 0:00 [kworker/1:2]
>
> I wonder if iostat actually communicates with the device driver at all? If
> not, then presumably it's looking at some kernel data structure. Maybe
> there is a lock being kept open on that by someone/something.
>
> At the same time, I notice that 'cat /proc/diskstats' still works, and
> starting a new 'iostat 5' process works too.
>
> After issuing halt -p I get this:
>
> root 34 0.6 0.0 0 0 ? D 11:29 1:18 [kswapd0]
> root 1258 0.0 0.0 15976 532 ? Ds 11:29 0:00 /usr/sbin/irqbalance
> root 1421 0.0 0.0 0 0 ? D 12:49 0:01 [xfsaild/md127]
> snmp 1430 0.0 0.0 48608 3440 ? D 11:29 0:00 /usr/sbin/snmpd -Lsd -Lf /dev/null -u snmp -g snmp -I -smux -p /var/run/snmpd.pid
> xxxx 1614 1.0 0.0 378860 3812 pts/1 D+ 12:50 1:15 bonnie++ -d /disk/scratch/test -s 16384k -n 98:800k:500k:1000
> xxxx 1669 1.1 0.0 378860 3816 pts/2 D+ 12:50 1:21 bonnie++ -d /disk/scratch/test -s 16384k -n 98:800k:500k:1000
> xxxx 1727 0.5 0.0 383424 692 pts/3 Dl+ 12:51 0:37 bonnie++ -d /disk/scratch/test -s 16384k -n 98:800k:500k:1000
> xxxx 1782 1.1 0.0 378860 3824 pts/4 D+ 12:51 1:20 bonnie++ -d /disk/scratch/test -s 16384k -n 98:800k:500k:1000
> xxxx 1954 0.0 0.0 5912 544 pts/0 D+ 12:58 0:00 iostat 5
> root 2642 0.1 0.0 0 0 ? D 13:25 0:09 [kworker/0:1]
> root 3233 0.0 0.0 5044 168 ? Ds 13:50 0:00 /usr/sbin/sshd -D -R
> root 4753 0.0 0.0 15056 928 ? D 14:42 0:00 umount /run/rpc_pipefs
> root 4828 0.0 0.0 4296 348 ? D 14:42 0:00 sync
> root 4834 0.0 0.0 8100 624 pts/6 R+ 14:50 0:00 grep --color=auto D
> root 29491 0.0 0.0 0 0 ? D 12:45 0:00 [kworker/1:2]
>
> I see even umount'ing rpc_pipefs is hanging. So this suggests there's some
> sort of global lock involved.
You need to provide the output of sysrq-W at this point ('echo w >
/proc/sysrq-trigger') so we can see where these are hung. the entire
dmesg would also be useful....
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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