Date: Tue, 26 Jan 1999 11:17:31 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Kevin Day <toasty@home.dragondata.com> Cc: hackers@FreeBSD.ORG Subject: Re: High Load cron patches - comments? Message-ID: <199901261917.LAA20783@apollo.backplane.com> References: <199901261853.MAA15095@home.dragondata.com>
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:I have a somewhat unusual setup, where I have a server that several hundred
:customers use, that has all of /home over an nfs mount, and each customer
:has quite a few cron jobs that they like to execute every ten minutes or so.
:
:The problem is that they all want to execute their cron jobs on a */10
:minute frequency, so on every minute ending in '0', I suddenly have cron
:spawning off a few hundred processes, bringing the machine's load average
:above 15.0, and saturating my NFS link for quite a while.
:
:No amount of pleading with my users did much good, since they were just
:following a template given to them by the software they were using.
We had similar problems at BEST, especially on older machines. In fact,
and this is quite amusing ... we ran into a /proc simultanious-access
crashing bug precisely because 30 users were running botcheck scripts
every 10 minutes. ( This was before we banned irc bots at BEST ).
I finally gave up trying to get users to put crons in random minutes.
My solution was:
vi /var/cron/tabs/*
(manually mix up the minutes boundry for jobs that people ran at
common points, like the top of the hour)
kill the cron process
restart it
That solved the problem pretty much permanently. Users tended to not
bother to change the crons back once I had edited them.
The other big problem is that some users just love running cron jobs
once a minute, and sometimes when a machine gets loaded their jobs
do not finish quickly enough and start building up. Weee!
Adding such uses to cron.deny and disabling their crontabs solves
the problem.
:Can I get comments/suggestions about this?
:
:Kevin
I like your idea. I think it is a good idea. I don't have time to
review the actual coding, though.
-Matt
Matthew Dillon
<dillon@backplane.com>
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