APM alert !!!!

[Stuart Hughes <sehughes@zentropix.com>]

I always knew that APM was bad news for realtime (as it does cli etc),
but I was not aware that gettting the APM info from proc was also a
disaster.  While running some jitter tests that normally give  +/- 7usec
on a quite machine, I did a cat /proc/apm, this pushed the upper limit
to 7milliseconds.  So beware, just running a little X helper like xapm
(now disapeared from the latest redhat) will cause your realtime to
miss-behave.

Conclusion:  If you have APM enabled at all, beware as your real-time
programs can go out to lunch (even things as innocent as plugging in the
power cable to your laptop).

Regards, Stuart