Multiple GPU's in blender


(FreeMind) #1

Hey there.
Question: How well does Blender 2.8 rending, Cycles or Eeevee, scale when using multiple GPU’s?

Would having two GTX 1080 make it ~2X faster? Or more like 1.5X faster?..


(Emir Sinan Gürlek) #2

Eevee doesn’t make use of multiple GPUs. Maybe in the future it will. Check this topic.

Cycles makes use of multiple GPUs. But 2 GTX 1080 won’t make it twice faster. It will be more like 1.5 times faster. Check this topic.


(mathieu) #3

It depends if you use denoiser or not. The denoiser really will eat a lot of the speedup you can expect. Partly due to it being optimized for big tile size and because the 2 or more gpus will have to exchange the tiles all the time to be able to denoise them (denoising requires the neighbour tiles to be seamless).
However, if you render animations and you have one instance of Blender per GPU, each one rendering a different frame, or if you render stills with small tiles, then it would scale pretty well (at 16x16 tiles, it scales nearly perfectly in my case)


(TiborNyers_BC) #4

It scales quite well, although it is not perfect as the tile-based distribution of the work is inherently difficult to balance. If the workload is even across the entire image / tiles, you can get pretty good scaling.


As @bliblubli mentioned, animation rendering can be issued per even / odd image per GPU if you have 2 of them.


#5

Is this doable with Eevee? Can you guys point to a tutorial / how-to somewhere that shows how to do this? Tried Googling for it, can’t find anything.


(Markus Mayer) #6

It might be possible if you connect each card to a different Monitor. Interesting thought…
Have to investigate.


(Casey) #8

I have some render test results for you to peruse. As far as scaling goes, it’s not perfect 100% scaling, but two identical cards will be approximately twice as fast as one. You will need 4 cards to halve that speed again. You would need 8 to halve it again, but again, scaling isn’t perfect and there are diminishing returns after a certain point. I run 6 GPUs for rendering so you can get an idea of how that works in the link below.


(FreeMind) #9

When I’ll be upgrading, I’m thinking on whether I should go for another GTX 1080, or get a newer Single card.
My guess was that 2 X GTX 1080 would be better than anything Nvidia would release any time soon…


(Casey) #10

Yeah for rendering purposes, you’re mainly concerned with how much compute power you have, and any potential VRAM limitations you might or might not run into. A 1080 is going to give you a good amout of VRAM headroom as long as you aren’t rendering huge files.

So, my 6 RX480s will run circles around a pair of 1080’s even though for single use…such as in a gaming situation, the opposite is true.