NetBSD domU crashing Debian5 dom0 with NMBCLUSTERS=4096

["Dirk H. Schulz" <dirk.schulz%kinzesberg.de@localhost>]

Hi folks,

I tested running Nagios in a NetBSD5 domU on a Debian5 dom0 (this is 
because our dom0s have to have bonded nics for redundance and this seems 
still to be a problem with NetBSD 5, as I understood).

We run several NetBSD 5 domUs on Debian5 dom0s, that is working fine so 
far with the standard NetBSD domU kernel.

But with the Nagios VM I ran into problems with "No buffer space 
available", so I recompiled the NetBSD domU kernel with NMBCLUSTERS = 4096.

This kernel repeatedly crashed the Debian dom0 kernel; I tested that on 
2 different servers (one dual PIII, where the crash happened within an 
hour, and one Dual Xeon 3.2 GHz, where the crashes took a few hours to 
happen).

At the moment this is simply a coincidence (as the Debian dom0 kernels 
crash every few weeks anyway), but in the case of the self built domU 
kernel the dom0 kernel crashes looked different: no error output, just a 
blank screen.
After disabling the self compiled kernel everything went back to normal.

First question of course is: Is it technically possible that the dom0 
kernel crashes are related to the NMBCLUSTERS parameter in the domU kernel?
Next one of course: Is this a known problem? Is there a workaround? I 
would very much love to test NetBSD as domU for high load use.

Dirk