Why is RTX slower than Cuda here?

[Micha]

Hi,

from time to time I give RTX a chance and enable it. But nearly always it's slower than Cuda. I render train interiors and exteriors often.


exterior
Cuda 2m:42s
RTX 3m:04s

interior
Cuda 13min33s
RTX 14min24s

I use 2x2080ti and one 3090 (the system card).

I can't believe that the RTX mode is so useless. Is something wrong with my setup? I'm working with V-Ray for Rhino (core version 5.10.04).

-Micha

[Paul Oblomov]

Yeah, mine rtx is two times slower than cuda. Surprised... but, maybe it is new reality, and vray gpu not going to move out of eternal pre alpha stage...

[Muhammed_Hamed]

Hi Micha

If you are using a recent Nvidia driver + recent V-Ray build you will see a boost in performance in Cuda mode, we worked with Nvidia on this recently. And even on older Vray 5 builds you will have a nice boost, for example the benchmark tool will show you much higher scores than before.
So we are aware of that, and it is expected to happen, the difference will be small like what you see in your case
And on the other hand we are working on improving the RTX mode as well, it is also a priority to us

I do testing regularly on both modes, most scenes still show a performance benefit on RTX mode. Rarely do I see a case where Cuda is ahead, and it is usually a small difference like your case

Paul Oblomov Being 2 times slower than Cuda is not expected, I haven't seen that.
Could you please share more information on your setup and Vray version. It will be helpful to follow along to troubleshoot this

Best,
Muhammed

[Paul Oblomov]

Yeah, it wasnt, but I just changed to cuda and 2.49 became 1.07. Very nice surprise here. About debugging - maybe later. Scene is so simple, that I'm sure you have something like this through all the scenes, that vray is testing against, before release.

edit
But non of this matters, since a bunch of errors.
// Error: line 1: V-Ray : C:CIcgrepovraysdksamplesvray_plugins
t_private
t_opencl_(2765) : CUDA error 700 //
// Error: V-Ray : [MemoryManagerGpu::releaseUnmappedMemoryFromInstanc e] 700: Could not release device buffer //
// Performing AutoSave at 2021/10/19 16:57:02:

edit2
LOL. Now, while cuda is faster it has broken materials. Only slower rtx renders like it should. Vray gpu "almost_pre-alpha" 5 maya from today and latest drivers. Now cuda 4 times faster, tho with broken materials I dunno, is there any review tests scenes, before nightly goes online? Why my pc is the only one, that got some troubles with vray gpu... Feels like devs pc are just rock solid stable war machines from future. I wasn't able to render anything, that is more complex, that two cubes with vray gpu in about a year or so. Curious, how others are rendering smth

[Muhammed_Hamed]

Hi Paul Oblomov

I'm sorry to hear about your experience, are you using a 3080 ti by any chance?
We are investigating issues with specific setups, using LHR GPUs 3070tis and 3080tis and yes most of the complaints are on Maya's IPR

About the testing, we have automated daily tests and I do my own testing with a bunch of production scenes of my own. I joined the Chaos team this month, prior to that I did concept design and 3D visualization in high-end print for about 6 years, mostly Automotive work and interior design
And yes Vray GPU is being used in production, I used V-ray GPU at Renntech, Carlex and bunch of other studios I worked at.. I will add that stability of V-Ray GPU is top priority to Chaos, and now I'm spending a lot of my time testing V-ray GPU in Maya

If you get a chance to test with my scene here , let me know if it crashes for you or if the RTX mode is slower than Cuda
Are you using a build from nightly or stable folders? what Maya version ? and what GPU and driver do you have?

Or if you get a chance to upload your simple scene, if it crashes for me I will follow along with you on getting this solved.. And same about the RTX slowdowns
Thanks!

Best,
Muhammed

[luisgamino2]

Hi Muhhamed

Which is the newest nvidea driver for vray gpu, mine is 471.05, i did a test RTX is by far faster than cuda almost 40% faster than cuda in interior scene and exterior scene... RTX is very fast much faster than cuda no doubt, vray 5.1 gpu for sketchup
i don't know why people complain about this, since the rtx release RTX is faster than cuda almost 40% or 50% faster, i almost don't use cuda... 2 2080ti with nvlink is great with RTX mode

Thanks

[Paul Oblomov]

Well, my rig is tr24cores/3090/256gb. Always new drivers and fresh builds. I tried scenes from benchmark rtx with recent drivers and 19th build is faster. Tried my own scene - broken material in cuda and it is 4 times faster, than rtx. Magic Will upload scene today.

[Micha]

I didn't a benchmark since a few months and downloaded the latest benchmark today. Is there really no test of RTX vs. Cuda based on the same scene?

[Paul Oblomov]

Of course there is. Just find vrscenes and use -rtEengine=5 or 7

[Paul Oblomov]

Ok. So as of today - I dunno, why it renders almost the same, except round edges. Rtx works, cuda - not. Yesterday I saw pure black pictures... Maybe I changed the build to 19-th. So the old one with new drivers - were surprisingly bad, but 19-th october release - almost working.

[Paul Oblomov]

So, they are working differently.

[Muhammed_Hamed]

Which is the newest nvidea driver for vray gpu, mine is 471.05

Hi Luis,

Newest recommended driver is 471.68
You can always go to the GPU page here, you will find the recommended driver at the top. Additionally you will find a message in the log if you have an old or newer driver than the recommended one

i did a test RTX is by far faster than cuda almost 40% faster than cuda in interior scene and exterior scene... RTX is very fast much faster than cuda no doubt, vray 5.1 gpu for sketchup

Thanks for the feedback, I have always used RTX mode when I worked in high-end print. That being said, both modes will evolve with time, they share most of the code

2 2080ti with nvlink is great with RTX mode

It is a great setup Luis, should be plenty fast

Best,
Muhammed

[Muhammed_Hamed]

Is there really no test of RTX vs. Cuda based on the same scene?

It depends on the scene, usually Optix is faster when you have hair/fur/grass. And in a rare case of being slower, the difference is small.
Both modes will evolve with time, we work closely with Nvidia on improving Optix and Cuda performance. Newer drivers are helpful for that as well
If you have a very good CPU, using Cuda makes more sense in that case. Other than that, I usually use RTX mode

Best,
Muhammed

[Muhammed_Hamed]

Yesterday I saw pure black pictures... Maybe I changed the build to 19-th. So the old one with new drivers - were surprisingly bad

Sometimes the GPU driver goes to this odd state, until you restart the machine or log out.
So this doesn't crash for you anymore?
is there a chance I can get this piece of geometry/scene, I will test with both builds and let you know what is going on.
Thanks!

Best,
Muhammed

[Paul Oblomov]

Sometimes the GPU driver goes to this odd state, until you restart the machine or log out.
So this doesn't crash for you anymore?
is there a chance I can get this piece of geometry/scene, I will test with both builds and let you know what is going on.
Thanks!

Best,
Muhammed

Here's one. Geo is restored alembic from h.