Roman Neuhauser wrote:
I have a problem with on of my FreeBSD boxes. All of a sudden, it
started acting very badly: any process takes ages to start completely,
eating all CPU in the process:

  852 root       57   0  1528K   996K RUN      0:19 91.95% 59.81% top

root@ishtar ~ 1017:0 # time ps auxww
ps auxww  0.00s user 0.01s system 0% cpu 2.197 total
root@ishtar ~ 1018:0 #
Looks like it's not eating up much of the computer's time to start, just
that something else is preventing it from accessing what it wants
immediately.  Could be starved from RAM, or waiting on a busy ATA controller
or any number of things.

compare a slower box:

root@lilith ~ 1005:0 # time ps auxww
ps auxww  0.00s user 0.02s system 64% cpu 0.036 total
root@lilith ~ 1006:0 #
Sounds like the faster box is bogged down with some task.  Maybe flushing
disk data?  What else is running on this box?

This strangeness lasted for about 20 minutes, persisted across a reboot
(I pulled out the wrong cable...), and then just disappeared; the box
works as it should.
You don't state the hardware either.  Lots of places a bottleneck could
occur that would make the system sluggish.

I know this is hard to asnwer, but what could have caused the effect,
and what should I be looking for if it happens again? There's nothing
especially interesting in /var/log/messages.
I've seen some processes suddenly grab a lot of the machine's ability and
bog it down temporarily.  Usually with a combination of top and systat, I
can identify where the load is coming from.
This is especially noticable in 5.0.  You don't say, but I'm assuming you're
running 4.x though.

BTW, top showed swap wasn't used at all.
Out of ram/swapping isn't the only place a machine can bog down.  What
applications are you running on it?
Does top show any other processes using a lot of CPU time?  A snapshot
of top output while the problem is occurring would be informational to
anyone trying to help.

Bill Moran
Potential Technologies

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