Constant 20% CPU load after upgrade to fc2

[Rud Holmgren]

Rud Holmgren wrote:
> 
> Having just upgraded my fc1 installation to fc2
> I experience that the CPU is constantly loaded
> at about 20% average. On the system monitor applet
> the load appears as spikes when using a 0.5 sec
> update interval. The spikes are neither regularly
> spaced nor equal in height. When running top in
> a terminal it reports the average user space load
> at about 20%, approx 1% system  load, and about
> 80% idle time. No process in the process list
> eat more than 1%-2%.
> 
> My guess is that some process is started regularly
> that eats up a lot of resources and then dies. I
> have tried catching this - without any luck. I
> have some of the kernel userspace helper threads
> under suspicion (a khelper). It's kind'a frustrating
> so I hope somebody has an idea at to what is
> happening.
> 
> 
> 
> /rud
> 


Well, after further investigation it turns out that
the kernel repeatedly tries to modprobe char_major_2_N
for a range of N's. It does it through the khelper
userspace kernel helper but with such high priority
that top can't catch it. I had to write my own little
piece of Ruby to catch it! The strange thing is that
nothing appears in the logs.

Device char major 2 is old-style (legacy bsd) tty masters
that are no longer supported by the kernel shipped
with fc2. I have a VERY old driver for a serial port
server (moxa) running that uses this mechanism. It is
run directly from /etc/inittab why I didn't find
straight away.


/rud