Hi,

I've been having a problem for a while but I've never been quite sure
if it was a problem with my system, a problem with NetBSD, or a
problem with XFree86.  Today I managed to get a little bit more useful
information, so I wanted to describe the problem, describe my
workaround, and find out if this was a known problem or if anyone has
any clues before I file a PR.

The system setup is:
486/66
16M RAM
3C509 NIC
ET4000/W32i EISA video card
Microsoft 2-button serial mouse
/, /usr, and swap on NFS (server has nearly identical configuration,
with more memory)
NetBSD-current (1.2G supped and built yesterday, but I've had this
problem since ~ 1.2D or E when I started using this machine)
XFree86 3.3, SVGA server (problem also appeared with 3.2A)

While running X on this box, I'd occasionally get a total freeze-up.
The machine totally wedges...can't do anything on X or via the
network.

The freezes seem to happen most often when the machine gets really
busy.  For example I can start one xterm with no trouble, but if I
start about 16 of them at once it is very likely to hang.

Sometimes starting (or using) one large program (e.g. Netscape) would
cause the hang.  This makes me think the problem is related to
swapping.

If I started a few xterms or started netscape, and wiggled the mouse
as it loaded via NFS, the mouse pointer would move very slowly in
large "hops", and the certainty of a crash approached 100%.  This
leads me to believe that the problem is related to lost interrupts.

As an experiment today, I added another disk to the machine (in its
original configuration the machine only had one disk entirely devoted
to MSDOS -- the kernel is netbooted) and put swap on this disk instead
of on nfs.

With this configuration, I haven't been able to produce a hang.  I put
the machine through a few torture tests, such as starting about 15
xterms or about 5 netscapes at once, over and over.  The machine
thrashed a lot, and once or twice I thought it was going to hang, but
it always "recovered" and went on working OK.

So...has anyone else seen similar problems when swapping via NFS?  Is
this a problem with NetBSD, or is it a problem with XFree86?

Thanks,
entropy

p.s. in case I stupidly left out some important configuration
information, you will find dmesg output and XF86Setup for this box at:
ftp://zippy.bernstein.com/pub/entropy/tanstaafl/

--
entropy -- it's not just a good idea, it's the second law.

This message may refer to a product containing software developed by
Christopher G. Demetriou for the NetBSD Project.