Speed of the second card 50%

[martin_petkov]

Hello i notice when i use 2 gpus the speed of the 2nd is about 50-60% of the speed of the 1st card do you have any plans to improve this? Thanks in advance!

[npg]

What do you call "speed"? What GPUs are you using? Vantage tries to automatically balance the load when using two GPUs.

[martin_petkov]

2 x 3090 what do you say that vantage balance the load and you get 100% speed of the second gpu?

[npg]

The load balancing is needed when the GPUs are different and also because of denoising, which only runs on the primary GPU. 100% is maybe too optimistic, but it should be over 90%, I think. 50% usage sounds too low and I don't know why. Is the GPU load low regardless of what you do or does it change depending on scene, settings, resolution, interactive vs offline?

[martin_petkov]

The two gous are on full load but the render is not two times faster not even 90%

[npg]

Oh, I see now what you mean. Adding a second GPU does not automatically mean it will render twice as fast. There are several factors:
- As I said, only one of the GPUs does the denoising.
- The light cache is automatically turned off because the algorithm does not work for multiple GPUs
- Depending on render resolution and render elements used, the link between the GPUs could be a bottleneck (PCI-e or Nvlink)

Do I understand correctly that you get roughly the same render times (or FPS) with one and with two 3090? You didn't give specifics.

[REDVERTEX]

Hi Nikola,

he means that We are getting the same render time on each card when rendering with single card. Let say 100 seconds. When the two cards are selected, the render time is not in half but about 75 seconds. This is probably because of the factors you already mentioned. We can confirm that using nvidia tools because one of the cards is drawing 25W lower and load is about 10-15%. Most likely becuase of the denoise.

We will be doing new test in the next few days with the latest versions of Vantage where the denoise is made only the final pass to check is there improvement.

Thanks.