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Date:      Wed, 9 Dec 2015 11:11:44 -0600
From:      Dustin Wenz <dustinwenz@ebureau.com>
To:        Jan Bramkamp <crest@rlwinm.de>
Cc:        freebsd-stable@freebsd.org
Subject:   Re: Periodic jobs triggering panics in 10.1 and 10.2
Message-ID:  <19A6FFCC-6B3A-44EB-B96F-D02F98364C3F@ebureau.com>
In-Reply-To: <56680148.9070601@rlwinm.de>
References:  <34FA7D40-8758-460D-AC14-20B21D2E3F8D@ebureau.com> <1449619470.31831.9.camel@michaeleichorn.com> <56680148.9070601@rlwinm.de>

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PF filed:

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D205163

Please let me know if there is any more useful information I can =
include.

	- .Dustin Wenz


> On Dec 9, 2015, at 4:24 AM, Jan Bramkamp <crest@rlwinm.de> wrote:
>=20
>=20
>=20
> On 09/12/15 01:04, Michael B. Eichorn wrote:
>> On Tue, 2015-12-08 at 16:31 -0600, Dustin Wenz wrote:
>>> I suspect this is a zfs bug that is triggered by the access patterns
>>> in the periodic scripts. There is significant load on the system =
when
>>> the scheduled processes start, because all jails execute the same
>>> scripts at the same time.
>>>=20
>>> I've been able to alleviate this problem by disabling the security
>>> scans within the jails, but leave it enabled on the root host.
>>=20
>> To avoid the problem of jails all starting things at the same time, =
use
>> the cron(8) flags -j and -J to set a 'jitter' which will cause cron =
to
>> sleep for a random period of specified duration (60 sec max). Cron
>> flags can be set using the rc.conf variable 'cron_flags'.
>=20
> While jitter would reduce the resource contention a thundering herd of =
cronjobs shouldn't cause the kernel to divide by zero. Spreading the =
load by introducing jitter to cronjobs might hide the problem, but it =
still needs further analysis.
>=20
> @Dustin Wenz: Can you reproduce the problem and file a PR to track =
this?
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