NMBCLUSTERS warning - sysctl fix?

[Donald Lee <MacPPC2%caution.icompute.com@localhost>]

I got a brief hang today on my production server running NetBSD 2.1 PPC:

Mar 24 13:57:07 mercy /netbsd: WARNING: mclpool limit reached; increase 
NMBCLUSTERS 
Mar 24 13:58:07 mercy /netbsd: WARNING: mclpool limit reached; increase 
NMBCLUSTERS 
Mar 24 14:00:08 mercy last message repeated 2 times
Mar 24 14:05:09 mercy last message repeated 5 times

In the NetBSD docs, there is some advice:

        http://netbsd.org/docs/kernel/#mclpool-limit

What I have done is set up /etc/sysctl.conf, and put:

        # Server gets busy sometimes.  Bump up network resources
        # number of "mbuf clusters"?  Default of 1024 too small.
        kern.mbuf.nmbclusters=4096

in it.  This seems to work fine, but I apparently have to bump it up again.

The docs (above) suggest the "sysctl -w", and also suggest patching the
kernel.  At the end of the section it says:

        Combining this, and patching the binary, would mean no need to
        build a new kernel or reboot.

Is there some reason that the sysctl.conf approach is insufficient?  Do I need
to set sysctl *and* patch the kernel for some reason?

Thanks,

-dgl-