Date: Wed, 9 Dec 2015 11:24:08 +0100 From: Jan Bramkamp <crest@rlwinm.de> To: freebsd-stable@freebsd.org Subject: Re: Periodic jobs triggering panics in 10.1 and 10.2 Message-ID: <56680148.9070601@rlwinm.de> In-Reply-To: <1449619470.31831.9.camel@michaeleichorn.com> References: <34FA7D40-8758-460D-AC14-20B21D2E3F8D@ebureau.com> <1449619470.31831.9.camel@michaeleichorn.com>
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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. >> >> I've been able to alleviate this problem by disabling the security >> scans within the jails, but leave it enabled on the root host. > > 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'. 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. @Dustin Wenz: Can you reproduce the problem and file a PR to track this?
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