The first thing to do is to compile up the latest 2.8.x kernel in
the release branch. Your freezes are probably related to a console
deadlock that we have fixed.
On swap use and memory use, we don't have enough information. 90%
of the bug reports related to memory use turn out to be
misinterpretations of system statistics, since DragonFly (like all
BSDs) use all available free memory to cache file data and drop the
cache as memory is needed.
If swap is growing unbounded over time and you are seeing constant
paging activity then it could be a runaway process running on your
machine, which you should be able to locate using miscellanious system
tools such as 'ps axl'.
-Matt