GPU still at 0% while rendering

RobertDy

It used to be that my CPU would be at 100% while GPU is at 0% while Iray rendering, so I unticked the Allow CPU option to make sure that only the GPU is working. Still though, now the CPU shows 30% while GPU's still at 0% (though the rendering's sped up and the CPU is less hot). Is there something I'm missing out? Thanks!

PerttiA

Task Manager at it's default settings doesn't show you the right charts.

The log will tell you if the GPU is doing it's job (Help->Troubleshooting->View Log File)

ebergerly

It's important that you use the correct measuring tools if you want to find out what's really going on. 

First, if you want to see if Iray is using your GPU to do rendering, you need to find out if the "CUDA Engine" is active. An "engine" is just a bunch of GPU cores brought together to perform some specialized function, in this case using CUDA to do the rendering (other engines are for copying data to and from the GPU and system RAM, encoding videos, etc.). To do this, you'll need to check the W10 Task Manager, in the Performance tab. During a render, select a GPU, then in the top left corner of the area with the 4 graphs, select the down arrow next to what probably says "3D" and select CUDA from the list. If the GPU is being used, the graph should be up near the maximum. Near the bottom of the graphs you'll also see one that says "Dedicated GPU memory usage", and that will tell you if the TOTAL VRAM usage across all processes is near the maximum available. If that graph is up near the maximum, it's possible that Windows will cancel the GPU rendering and it will fall back to the CPU and system RAM.

Second, you need to make certain that what you're focusing on D|S, and not the many other applications that can use the GPU's engines and VRAM. To do that, go into the Details tab, and in the column headers that say "Name, PID," etc., right click and select "select columns", and choose any title with "GPU" in the title. This will tell you what resources (GPU engines, VRAM, system RAM, etc.) each of the many applications/processes are using in real time.

By bouncing between those tabs you should get a good idea of actually what's going on. Keep in mind that there might be a dozen or so processes using your GPU and the various engines at any time, so it's important that you focus only on D|S.