The wiki is back up and running. I tested the Alien Map function on my 6000x4000 16-bit image, since according to the wiki, Alien Map uses open CL.
Again, it was slower with Open CL enabled. (10.2 seconds with Open CL enabled, 9.3 seconds with it disabled). I have 16 GB of RAM, by the way, and not using any swap space, if that matters.
Note that I’m not actually applying the changes, just previewing them, then removing the preview to time it to go back to normal.
I wonder if other people show a performance detriment with hardware acceleration. Could it be a bug? Or maybe I need to go to a linux forum and ask for help with my graphics drivers.