Thanks for the replies. Testing with the GEGL unsharp mask filter, htop shows my 16 cores at the top of the screen. They all spike up to around 40% processor usage while it’s doing the unsharping. Htop looks the same as far as CPU usage goes whether Open CL is enabled in GIMP preferences, or not.
The Gimp system resources preferences already tell it to use all 16 of my CPU cores.
Here are partial results of “clinfo.” There is more, but this seemed like the important part:
Platform Name NVIDIA CUDA
Number of devices 1
Device Name GeForce GTX 960
Device Vendor NVIDIA Corporation
Device Vendor ID 0x10de
Device Version OpenCL 1.2 CUDA
Driver Version 384.130
Device OpenCL C Version OpenCL C 1.2
Device Type GPU
Device Profile FULL_PROFILE
Device Topology (NV) PCI-E, 0b:00.0
Max compute units 8
Max clock frequency 1367MHz
Compute Capability (NV) 5.2