OpenBSD box freezes with: "/bsd: WARNING: mclpool limit reached; increase NMBCLUSTERS"

When I tried to run databases on OpenBSD, I encountered an issue running out of a resource that I didn’t quite understand at the time. I asked the following question on the list:

>  I get the "/bsd: WARNING: mclpool limit reached; increase NMBCLUSTERS">  messages "last message repeated 10 times" and then kernel panic and freeze.

I got the following response from Dries Schellekens email: gwyllion at ulyssis.org

From options(5)

option NMBCLUSTERS=value     Size of kernel mbuf cluster map, mb_map, in CLBYTES-sized logical pages.     Defaults to 2048 on i386, to 1024 on powerc and sparc64, and to 512 on     other architectures (doubled when using option GATEWAY'' except on     i386).  See /usr/include/machine/param.h for exact default information.     Increase this value if mclpool limit reached'' messages appear

You can easily increase the NMBCLUSTERS using config.

# config -ef /bsdukc> nmbclust 4096ukc> quit

If you still get these message, you could increase NMBCLUSTERS to 8192.