There was a thread on the -dev list with someone else having slowness on Ubuntu 16.04 with OpenCL on nVidia and it looked like a driver issue. They switched from version 361 of the nVidia driver to 340 and saw an improvement, might be worth trying.
Thread here: https://www.mail-archive.com/darktable-dev@lists.darktable.org/msg01176.html ____________________________________________________________________________ darktable user mailing list to unsubscribe send a mail to darktable-user+unsubscr...@lists.darktable.org
