page fault in kernel

[Tim Newsham]

I have an amd64 box that is occasionally panic'ing with a kernel
page fault while the system is under heavy load.  I tried swapping
out ram and running ram tests and that hasn't seem to turn up
anything.  I originally saw this with 8.1 but I recently updated to
8.2 to be sure and I'm still seeing the problem.  I'm up to date
with "freebsd-update" and I verified that the core files all match
the md5 of a clean 8.2 release (after it is also updated).  I also
tried to disable various frills I had installed (like ip6 tunnel).

The normal way I repro this issue is to start a "portupgrade -caP"
going and I usually get a crash within a few hours.  Sometimes
I see some unusual behavior instead of or right before a crash
(ie. program segfaults that shouldn't normally).

Are there any known kernel issues that sound similar to this
problem?  I've been working under the assumption that this is
probably hardware related, but I haven't yet ruled out software.

I'll probably be trying some tests with cpuburn.  Any other advice
for tracking down this issue would be appreciated.

Tim