rand_harvestq at 100% RELENG_11

[Mike Tancsa]

Not sure if this is normal behaviour or not, but on a recent RELENG_11
r321624, I noticed something odd about rand_harvestq.
While doing some disk stress testing of zfs, I was creating a bunch of
random files.
eg

dd if=/dev/urandom > /tmp/junk2 bs=1m count=10000

If I create enough of them, rand_harvestq seems to get pegged at 100% on
one of my CPUs

last pid:  1014;  load averages:  1.36,  0.96,  0.65
                                           up 0+00:17:00  14:22:45
49 processes:  3 running, 45 sleeping, 1 waiting
CPU:  0.0% user,  0.0% nice, 24.8% system,  0.0% interrupt, 75.2% idle
Mem: 24M Active, 4140K Inact, 12G Wired, 4001M Free
ARC: 11G Total, 3144K MFU, 11G MRU, 64K Anon, 19M Header, 1224K Other
     11G Compressed, 11G Uncompressed, 1.00:1 Ratio
Swap: 40G Total, 40G Free

  PID USERNAME    THR PRI NICE   SIZE    RES STATE   C   TIME    WCPU
COMMAND
   11 root          4 155 ki31     0K    64K CPU0    0  55:37 302.56% idle
   16 root          1 -16    -     0K    16K CPU3    3  10:39 105.60%
rand_harvestq
 1014 root          1  20    0  7892K  2668K CPU2    2   0:00   0.03% top

And it stays there

# ps auxwS | head -5
USER      PID  %CPU %MEM   VSZ  RSS TT  STAT STARTED     TIME COMMAND
root       11 295.2  0.0     0   64  -  RL   14:05   59:05.25 [idle]
root       16 100.0  0.0     0   16  -  RL   14:05   11:48.24
[rand_harvestq]
root        0   0.0  0.1     0 8400  -  DLs  14:05    0:08.96 [kernel]
root        1   0.0  0.0  5408  588  -  ILs  14:05    0:00.84 /sbin/init

Any idea whats going on ? The box is pretty standard

CPU: Intel(R) Xeon(R) CPU E3-1220 v3 @ 3.10GHz (3092.90-MHz K8-class CPU)

11.1-STABLE FreeBSD 11.1-STABLE #1 r321624 AMD64

KERNEL is non generic, but it just has a bunch of ethernet drivers
removed and pf and pflog added.

	---Mike


--





-- 
-------------------
Mike Tancsa, tel +1 519 651 3400
Sentex Communications, mike at sentex.net
Providing Internet services since 1994 www.sentex.net
Cambridge, Ontario Canada   http://www.tancsa.com/