tom arnall wrote:
On Saturday 26 August 2006 23:11, Raseel Bhagat wrote:
Hi,
On 8/27/06, mike@xxxxxxxxxx <mike@xxxxxxxxxx> wrote:
On Sat, 26 Aug 2006 12:55:33 -0700
tom arnall <kloro2006@xxxxxxxxx> wrote:
My system hangs momentarily every 4 mins 2 secs. The event coincides
with a 'top' entry in which 'events/0' grabs 50-95% of cpu capacity.
How can I determine what is causing the event?
This is a long-shot but the last time I had the same problem it turned
out that there had developed a loose connection with the heat-sink and
processor on the motherboard.
As a result, the processor used to over-heat in about every 3 minutes
or so, the watchdogs would come into picture and cause the machine to
hang or reboot.... usually reboot.
Just give a quick check on your hardware before probing into the software
side.
how did you identify the problem with the heat sink?
is it likely that a hardware problem would cause the hanging phenomenon at
such a precise interval? i ran 'top' in batch mode to a file for ~.5 hour and
also wrote down the time whenever the hang occurred, then i compared the
output of top with the 'hang moments'. there was an exact coincidence
with 'top' entries in which 'events/0' was gobbling the cpu. and these events
occurred exactly 4 mins 2 secs from each other.
i also logged the content of /proc/interrupts at intervals of ~.2 sec's. in
this case, there was no change at the 'hang moments' except that i got only 1
sample for the second in which the hang occurred. in all other cases, of
course, i got 5 samples per second.
thanks in advance,
tom arnall
north spit, ca
Tom -- You are right to be skeptical about the heat-sink suggestion.
I've had problems similar to that one, and they ALWAYS cause either a
reboot or a permanent hang (possibly with a kernel OOPS). They neve
cause the sort of transient problem you describe.
What you are seeing isn't really a "hang"; it is just the system
becoming busy with a task other than the one currently onscreen. The 2
seconds part intrigues me; might it be the case that the "hang" lasts
for 2 seconds? Or might the clock be 2 seconds off after it occurs?
(Hard to check from one instance, but over a day, this would lead to a
6-minute clock drift, easy to spot.)
I'm pretty sure "events" are what older kernels identify as keventd, a
process internal to the kernel. That is, you're seeing a line in top
something like this one ...
4 root 10 -5 0 0 0 S 0.0 0.0 0:00.00 events/0
... except that the %CPU column is a lot higher.
If I'm right, and if you're using a 2.6.x kernel, then you might see if
the application systemTap will help you to diagnose the problem. You
might also check if any cron job is running on this 4-minute cycle.
The other obvious suspects here are device drivers. Does lsmod show
anything running that's out of the ordinary? Do you have WiFi running on
this system (if som using what deirvers)?
Finally, 50-95% is a pretty big range. It makes me wonder if there is
ALSO some process grabbing a lot of CPU (the other 50%, when this value
is low) on a regular basis. Do you see anything in top?
If none of this helps, and/or if any of my guesses have been wrong, you
might post again with a more complete description of the system, namely:
what distro and version, what kernel ("uname -a" usually is enough), and
what type and speed of CPU. The output of "free" is sometimes
instructive as well. And what is the typical system load (1.00 - the
"id" value as reported by top on its third line)?
Oh, and you you use this system for anything other than the usual sorts
of desktop and server uses?
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