Quoting Steve Wills <swi...@freebsd.org> (from Tue, 22 May 2018 08:17:00 -0400):

I may be seeing similar issues. Have you tried leaving top -SHa running and seeing what threads are using CPU when it hangs? I did and saw pid 17 [zfskern{txg_thread_enter}] using lots of CPU but no disk activity happening. Do you see similar?

For me it is a different zfs process/kthread, l2arc_feed_thread. Please note that there is still 31 GB free, so it doesn't look lie resource exhaustion. What I consider strange is the swap usage. I watched the system and it started to use swap while there were >30 GB listed as free (in/out rates visible from time to time, and plenty of RAM free... ???).

last pid: 93392; load averages: 0.16, 0.44, 1.03 up 1+15:36:34 22:35:45
1509 processes:17 running, 1392 sleeping, 3 zombie, 97 waiting
CPU:  0.1% user,  0.0% nice,  0.0% system,  0.0% interrupt, 99.9% idle
Mem: 597M Active, 1849M Inact, 6736K Laundry, 25G Wired, 31G Free
ARC: 20G Total, 9028M MFU, 6646M MRU, 2162M Anon, 337M Header, 1935M Other
     14G Compressed, 21G Uncompressed, 1.53:1 Ratio
Swap: 4096M Total, 1640M Used, 2455M Free, 40% Inuse

PID JID USERNAME PRI NICE SIZE RES STATE C TIME WCPU COMMAND 10 0 root 155 ki31 0K 256K CPU1 1 35.4H 100.00% [idle{idle: cpu1}] 10 0 root 155 ki31 0K 256K CPU11 11 35.2H 100.00% [idle{idle: cpu11}] 10 0 root 155 ki31 0K 256K CPU3 3 35.2H 100.00% [idle{idle: cpu3}] 10 0 root 155 ki31 0K 256K CPU15 15 35.1H 100.00% [idle{idle: cpu15}] 10 0 root 155 ki31 0K 256K RUN 9 35.1H 100.00% [idle{idle: cpu9}] 10 0 root 155 ki31 0K 256K CPU5 5 35.0H 100.00% [idle{idle: cpu5}] 10 0 root 155 ki31 0K 256K CPU14 14 35.0H 100.00% [idle{idle: cpu14}] 10 0 root 155 ki31 0K 256K CPU0 0 35.8H 99.12% [idle{idle: cpu0}] 10 0 root 155 ki31 0K 256K CPU6 6 35.3H 98.79% [idle{idle: cpu6}] 10 0 root 155 ki31 0K 256K CPU8 8 35.1H 98.31% [idle{idle: cpu8}] 10 0 root 155 ki31 0K 256K CPU12 12 35.0H 97.24% [idle{idle: cpu12}] 10 0 root 155 ki31 0K 256K CPU4 4 35.4H 96.71% [idle{idle: cpu4}] 10 0 root 155 ki31 0K 256K CPU10 10 35.0H 92.37% [idle{idle: cpu10}] 10 0 root 155 ki31 0K 256K CPU7 7 35.2H 92.20% [idle{idle: cpu7}] 10 0 root 155 ki31 0K 256K CPU13 13 35.1H 91.90% [idle{idle: cpu13}] 10 0 root 155 ki31 0K 256K CPU2 2 35.4H 90.97% [idle{idle: cpu2}] 11 0 root -60 - 0K 816K WAIT 0 15:08 0.82% [intr{swi4: clock (0)}] 31 0 root -16 - 0K 80K pwait 0 44:54 0.60% [pagedaemon{dom0}] 45453 0 root 20 0 16932K 7056K CPU9 9 4:12 0.24% top -SHaj 24 0 root -8 - 0K 256K l2arc_ 0 4:12 0.21% [zfskern{l2arc_feed_thread}] 2375 0 root 20 0 16872K 6868K select 11 3:52 0.20% top -SHua 7007 12 235 20 0 18017M 881M uwait 12 0:00 0.19% [java{ESH-thingHandler-35}] 32 0 root -16 - 0K 16K psleep 15 5:03 0.11% [vmdaemon] 41037 0 netchild 27 0 18036K 9136K select 4 2:20 0.09% tmux: server (/tmp/tmux-1001/default) (t 36 0 root -16 - 0K 16K - 6 2:02 0.09% [racctd] 7007 12 235 20 0 18017M 881M uwait 9 1:24 0.07% [java{java}] 4746 0 root 20 0 13020K 3792K nanslp 8 0:52 0.05% zpool iostat space 1 0 0 root -76 - 0K 10304K - 4 0:16 0.05% [kernel{if_io_tqg_4}] 5550 8 933 20 0 2448M 607M uwait 8 0:41 0.03% [java{java}] 5550 8 933 20 0 2448M 607M uwait 13 0:03 0.03% [java{Timer-1}] 7007 12 235 20 0 18017M 881M uwait 0 0:39 0.02% [java{java}] 5655 8 560 20 0 21524K 4840K select 6 0:21 0.02% /usr/local/sbin/hald{hald} 30 0 root -16 - 0K 16K - 4 0:25 0.01% [rand_harvestq] 1259 0 root 20 0 18780K 18860K select 14 0:19 0.01% /usr/sbin/ntpd -c /etc/ntp.conf -p /var/ 0 0 root -76 - 0K 10304K - 12 0:19 0.01% [kernel{if_config_tqg_0}] 31 0 root -16 - 0K 80K psleep 0 0:38 0.01% [pagedaemon{dom1}] 0 0 root -76 - 0K 10304K - 5 0:04 0.01% [kernel{if_io_tqg_5}] 7007 12 235 20 0 18017M 881M uwait 1 0:16 0.01% [java{Karaf Lock Monitor }] 12622 2 88 20 0 1963M 247M uwait 7 0:13 0.01% [mysqld{mysqld}] 27043 0 netchild 20 0 18964K 9124K select 6 0:01 0.01% sshd: netchild@pts/0 (sshd) 7007 12 235 20 0 18017M 881M uwait 8 0:10 0.01% [java{openHAB-job-schedul}] 7007 12 235 20 0 18017M 881M uwait 6 0:10 0.01% [java{openHAB-job-schedul}]


On 05/22/18 04:17, Alexander Leidinger wrote:
Hi,

does someone else experience deadlocks / hangs in ZFS?

What I see is that if on a 2 socket / 4 cores -> 16 threads system I do a lot in parallel (e.g. updating ports in several jails), then the system may get into a state were I can login, but any exit (e.g. from top) or logout of shell blocks somewhere. Sometimes it helps to CTRL-C all updates to get the system into a good shape again, but most of the times it doesn't.

On another system at the same rev (333966) with a lot less CPUs (and AMD instead of Intel), I don't see such a behavior.

Bye,
Alexander.

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