psconfig running excessively long

I’m trying to add the March CU to my SharePoint 2013 farm. After the bits are installed I'm trying to run the config wizard but the final step (9 of 10) runs excessively long. I left it running on VM for 6 days before killing it. It doesn’t error out but it appears the thread priority of the process keeps getting bumped down (see log entries below). I’ve stopped some of the services (timer, search and host controller) but doesn’t seem to help.

Any ideas?

psconfig: Yielding psconfig session on current thread to allow the admin service to run upgrade in the background.

psconfigui (0x0FB0)         0x1268  SharePoint Foundation Upgrade              SPUpgradeSession         ajxli        INFO               Yielding upgrade session on current thread,