10-STABLE hangups frequently

Peter Jeremy peter at rulingia.com
Tue Feb 2 20:07:55 UTC 2016

On 2016-Feb-02 16:55:46 +0900, Hajimu UMEMOTO <ume at mahoroba.org> wrote:
>I'm disturbed by a frequent hangup of my 10-STABLE boxes since this
>year.  It seems occur during running the periodic daily scripts.
>I've narrowed which commit causes this problem.  It seems r292895
>causes it.  I see many `Resource temporarily unavailable' message just
>before hangup occurs.
>Any idea?

As others have said, you need to provide lots more detail on your

That said, I'm seeing something potentially similar on a Google
Compute Engine f1-micro instance (1 vCPU, 0.6GB RAM) that is running
FreeBSD 10-stable/amd64 with ZFS but basically idle.  (Yes, I realize
that's very little RAM for ZFS but I previously had no problems with
things like buildworld).

There were no problems at r290231 but after I upgraded to r295005, I
started seeing "out of swap" errors and hangs during the periodic
daily runs.  I'm not seeing this on 1GB instances - though they are
all running UFS.

Some experimentation suggested that just "find /" was enough to wedge
my system.  I did some experimenting and found that the following
loader config was enough to prevent it hanging:
(previously, I had no ZFS tuning at all).

One odditity was that I would semi-regularly see:
 kernel: pid 67431 (ntpd), uid 0, was killed: out of swap space
I haven't worked out why the OOM killer preferred ntpd to anything else -
it didn't seem to be bigger.  And I didn't see any signs that swap space
was being consumed (though I haven't done a scientific examination).
(Note that swap is on a raw partition).

The behaviour is definitely a regression and my initial suspicion is ZFS,
though I haven't identified any smoking gun.

Unfortunately, GCE only offers read access to the console, so I can't
use DDB to poke around after it wedges.

Peter Jeremy
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