Jails on ZFS yielding 100% load on gstat

[Alan Somers]

Jails probably aren't the source of your problem.  You need to find out
what process or processes are responsible for all this activity.  Since the
write bandwidth is fairly low, you might have a process that's sync(2)ing
or fsync(2)ing. too often.  "gstat -o" will show if that's the case.  You
can also try running "top -mio" to see which processes are doing the most
I/O.

-Alan

On Sun, Aug 12, 2018 at 12:50 PM, Marco Steinbach <
coco at executive-computing.de> wrote:

> Hi there.
>
> % zpool list
> NAME    SIZE  ALLOC   FREE  EXPANDSZ   FRAG    CAP  DEDUP  HEALTH  ALTROOT
> zroot  5.41T   670G  4.75T         -    13%    12%  1.00x  ONLINE  -
>
> % uname -a
> FreeBSD XXX 11.1-STABLE FreeBSD 11.1-STABLE #0 r322984 [...] amd64
>
>
> I'm running multiple jails on ZFS, using ezjail to manage them,
> including a websever and a mailserver. The mailserver is using a MySQL
> database, otherwise depending on dovecot and postfix. Very low volume,
> just a few polls / logins per minute.
>
> I am experiencing very high loads as per gstat:
>
> dT: 1.021s  w: 1.000s
>  L(q)  ops/s    r/s   kBps   ms/r    w/s   kBps   ms/w   %busy Name
>     4    181      0      0    0.0    169    873   20.1   98.2| ada0
>     2    111      0      0    0.0    100    540    7.3   90.6| ada1
>     0     88      0      0    0.0     76    458    1.4   43.3| ada2
>     0      0      0      0    0.0      0      0    0.0    0.0| ada0p1
>     3    150      0      0    0.0    150    603   20.2   95.1| ada0p2
>     1     31      0      0    0.0     20    270   19.2  117.0| ada0p3
>     0      0      0      0    0.0      0      0    0.0    0.0| gpt/gptboot0
>     0      0      0      0    0.0      0      0    0.0    0.0| ada1p1
>     1     85      0      0    0.0     85    341    8.4   68.9| ada1p2
>     1     25      0      0    0.0     15    200    0.9   75.0| ada1p3
>     0      0      0      0    0.0      0      0    0.0    0.0| ada2p1
>     0     62      0      0    0.0     62    251    1.6    9.9| ada2p2
>     0     26      0      0    0.0     15    208    0.5   42.0| ada2p3
>     0      0      0      0    0.0      0      0    0.0    0.0| gpt/gptboot1
>     0      0      0      0    0.0      0      0    0.0    0.0| gpt/gptboot2
>
>
> These loads lead to the system suffering from very much delayed
> responses to even the basic task of echoing characters entered on the
> console, consequently rendering the services offered unusable to the
> users because of the delays.
>
> Restarting the jails (or even the whole machine at that) ends me up at
> exactly the same situation.
>
> I do have lab machines for running load scenarios, so if anyone feels
> compelled to lend a hand, please do.
>
> MfG CoCo
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