I was trying to calculate DivV and Vorticity for some big runs and it was taking too long, so after a bit of effort I pushed a change today (97262a5a252b) that speeds up ghost zone calculation in my (admittedly pathological) tests by about a factor of four. It's now dominated by IO and by the actual refinement process (FillRegion). There are a few other low-hanging optimizations I may attempt to apply.
The results are bitwise identical to the old results for all of my tests, but if you see anything odd, please let me know. It's not clear to me that behavior at cell edges is correct during the *process* of refinement, which I noticed for the first time when doing this. If somebody else wants to take a look at this -- Sam I know in particular has looked at the ghost zone code in the past -- it'd be appreciated.