Posted by Wade Walker on Jul 03, 2015; 7:00pm
URL: https://forum.jogamp.org/Dual-GPU-7990-card-not-using-both-GPUs-concurrently-tp4034813p4034817.html

Hi Joe,

Looking at the code for clWaitForEvents(), all it does is check the buffer arguments to make sure they're direct buffers, and then call the native OpenCL function, so there shouldn't be any waiting in the JOCL wrapper. Same goes for clEnqueueNDRangeKernel().

On Stack Overflow and other forums I've seen people saying that clEnqueueNDRangeKernel() is a blocking call on Nvidia hardware, even though the OpenCL spec doesn't require this. The Stack Overflow guy even got a response from Nvidia telling him to enqueue in separate threads :) So it looks like this is an Nvidia thing.

http://stackoverflow.com/questions/11562543/clenqueuendrange-blocking-on-nvidia-hardware-also-multi-gpu
https://devtalk.nvidia.com/default/topic/415023/launch-kernels-in-parallel-/