Little bit of a gotcha for zfs with gjournal.

This is more for the archives than anything else.
I have my home server build as a gmirror / and zfs for the rest, I was
having regular kmem_map too small panics when building port even after
putting in the various zfs tuning suggestions. I was thinking I must
have a hardware issue or something weirder as the issue appeared after I
added WRKDIRPREFIX= pointing to a new disk that wasnt on the zfs mirror
(formatted ufs2 with gjournal) after i managed to panic the box building
openoffice on the zfs (hadnt managed to panic it in a few months prior
to that.)
The problem I was having I finally managed to track down (I believe) to
the fact that the default value of kern.geom.journal.cache.limit was
high enough that when I started the build of the jdk15 port I was
hitting the kmem limit by the combined efforts of zfs and gjournal.
fixed by taking the value of kern.geom.journal.cache.limit down.

Panic String: kmem_malloc(131072): kmem_map too small: 388349952 total
allocated

Like I said not a bug, more a tuning hint. Hope someone finds this
useful although I cant see it being a common configuration.

Vince