Rendering with AI Denoiser is extremely slow.

[Yamen]

I don't know if this is a bug but what's happening is that when I turn the denoiser on it slows down the render from about 5-6 ms/sec to 0.1 ms/sec and slows down the whole system (denoise on completion is on) this isn't happening on one specific scene, I tried it with several scenes.
I should say that I have one GTX 970 and 2x6 core Xeon 48 GB RAM and the latest Octane for C4D
The problem isn't consistent, this doesn't happen every time I turn the denoiser on but about 60% of the time
as an example: The other day I started a render overnight with the denoiser on and Octane was finishing frames with around 6 minutes at around 6 ms/sec
render settings

The next day I get a crash then when I restart and try to render the remaining frames with the exact same settings I get 0.1 ms/sec 4 hours a frame I turn the denoiser off and it's up to speed back on and it slows down. I tried several things, I noticed sometimes when I reset the settings then modify them back to where they were, does the trick but not every time. sometimes when I switch to PMC and back to PT it starts working fine again. sometimes, I switch to a camera that has denoiser off and the speed bounces back up, I tried the stop and reset render data but no luck. sometimes nothing works until I turn the denoiser off.

with denoiser on

with denoiser off

any thoughts?

[aoktar]

Try with "denoise on completion". Otherwise it will slowdown.

[Yamen]

Thanks for your reply but as I mentioned the "denoise on completion" is on, I never turned it off. Even if it's turned off I wouldn't expect a slow down by 60 fold. I noticed that there's a correlation between the used Vram and this issue but I might be wrong.

[bepeg4d]

Hi,
from your screenshots, you are having issues with memory.
When you have long rendering time, you also have Out-of-core active, that means that VRAM is finished.
Please note that 970 has only 3.5GB of VRAM , not 4GB, Windows takes ~19% of VRAM, AI Denoiser needs ~500MB,... so you end up to have very few memory to work with, roughly ~2GB.
You need to extremely optimize your scenes to use less memory as possible, or it is time to switch to a more powerful GPU.
ciao Beppe

[Yamen]

Thanks Beppe, that makes sense.