[tlug] CPU monitor shows 100% use, but process list shows nothing above 10%

[Dave M G <martin@example.com>]

TLUG,

On my Gnome panel, I have a little icon that continually shows my 
processor use. If I click on it, the Gnome System Monitor comes up, 
showing the active process.

This morning when I woke up, I heard the CPU fan on my computer running 
really loudly. So I sat in front my computer to determine what was going 
on. Usually, Bittorrent is the culprit. Sometimes if I leave it on for a 
while, it starts sucking up CPU cycles, even if there's nothing downloading.

But, even after shutting down every open application the CPU was still 
running loudly and showing 100% use in the monitor icon.

So I click to get the Gnome System Monitor, and I click on the column 
marked "%CPU" to see which processes are most active.

Most are in sleeping status and show a 0% CPU usage. The Gnome System 
Monitor, now that it is open, is using about 10% or so. But nothing else 
is using much, if any CPU time. Even if I add up the few processes that 
are using tiny bits of CPU processing, it's nowhere near the 100% that 
I'm seeing and hearing. It's not even over 20%.

Eventually I rebooted, and the CPU went back to its usual quiet status.

But this has actually happened before, and this time I'd like to get to 
the bottom of it. My questions are basically:

1. Why is there a discrepancy between the list of processes, and the CPU 
monitor (and the fact that I can hear the CPU working at maximum)?

2. When this happens again is there a better way of querying what 
processes are running so that I'm more likely to find the process that's 
hogging the CPU?

Thanks for any advice or information.

--
Dave M G
Ubuntu Feisty 7.04
Kernel 2.6.20-15-386