Date: Tue, 26 Jan 1999 18:08:58 -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: <199901270208.SAA27656@apollo.backplane.com> References: <199901270144.TAA27675@home.dragondata.com>
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:>
:> 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
:>
:
:Tried that, but it doesn't stay fixed long enough, and we've had the
:occasional disgruntled user put 5000 'find /'s in his crontab and watch the
:machine explode.
Woa! It's trivial to handle that situation, just give your users
reasonable resource limits.
All of BEST's users are placed in the 'standard' class. I then have
a 'standard' entry in /etc/login.conf that gives them reasonable resource
limits.
It's possible that due to the way cron works, the resource limits is not
being held to, but since cron runs a shell script and that runs the find,
the resource limits should be held to. If not, we can fix cron.
We occassionally had some idiot IRC hacker login and try to take down
the machine from a shell prompt, usually with a fork attack, but since
we've put in the resource limits they've never been able to do it. It's
quite amusing. I gave rather generous resource limits -- normal users
usually don't even know they are there.
:> 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!
:
:Yep. This patch seems to fix that. It queues jobs up. After it reaches a
:huge number of queued jobs, it starts doubling the execution rate. Every
:time you double the maximum number of allowable jobs in the queue, you
:double the run speed. Very coarse, but it does self tune to catch up.
:
:Kevin
-Matt
Matthew Dillon
<dillon@backplane.com>
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