I have a machine where I enabled swap on ZFS somewhat accidentally (really wanted to dump to ZFS, but that didn't pan out) and then forgot about it. A month later, under a heavy load (make -j8 buildworld) it hung with: swap_pager: indefinite wait buffer: bufobj: 0, blkno: 289218, size: 4096 swap_pager: indefinite wait buffer: bufobj: 0, blkno: 290789, size: 4096 swap_pager: indefinite wait buffer: bufobj: 0, blkno: 305343, size: 4096 <...> scrolling on console. I made 2 more attempts to buildworld before I finally remembered the ZFS swap partition and removed it, which allowed the buildworld to complete without hanging the machine. It is running 8.0-STABLE #1 r205446M (amd64) and has very little (512MB) RAM. Drew