How to enable NVLink in OR 2018.1 XB1 ?

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How to enable NVLink in OR 2018.1 XB1 ?

Postby linvanchene » Wed Dec 05, 2018 10:13 am

linvanchene Wed Dec 05, 2018 10:13 am
How do I enable NV Link in Octane Render 2018.1 XB1?

System

Win 10 Pro 64bit
Intel Core i7 5820K
ASUS X99-E WS
64 GB RAM


2x ASUS GeForce RTX 2080 Ti TURBO
Asus NVLink Bridge 4-Slot

Nvidia Driver Version: 417.22

Steps performed:

- installed Asus NVLink Bridge 4-Slot

Asus NV Link Bridge 4-Slot.jpg
Asus NV Link Bridge 4-Slot


2x RTX 2080 Ti - NV Link 4 Slot.jpg
2x RTX 2080 Ti - NV Link 4 Slot


- reinstalled Nvidia driver 417.22 (clean installation)

- checked SLI status in Nvidia Control Panel: SLI enabled

RTX 2080 Ti - Sli enabled.jpg
RTX 2080 Ti - Sli enabled


- Octane Render 2018.1 XB1 - Preferences - Devices

tried to assign a Peer

Preferences - Devices - Peer.jpg
Preferences - Devices - Peer


Unfortunately still at VRAM 11264 MB

VRAM 11264 MB.jpg
VRAM 11264 MB


I expected available VRAM to change to ~ 22'000 MB.

- - -



Based on the image shared in the Development build releases thread there seems to be a NVLink Quicktest but I do not know how to access that.

Image

Source:
viewtopic.php?f=33&t=69461

- - -

Any ideas?
I tried to search the forum but did not find any further information.

- - -
Win 10 Pro 64bit | Rendering: 2 x ASUS GeForce RTX 2080 Ti TURBO | Asus RTX NVLink Bridge 4-Slot | Intel Core i7 5820K | ASUS X99-E WS| 64 GB RAM
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Re: How to enable NVLink in OR 2018.1 XB1 ?

Postby abstrax » Sun Dec 16, 2018 9:04 pm

abstrax Sun Dec 16, 2018 9:04 pm
The statistics in the viewport don't show the memory that is available by using the other GPU. You will have to run out of memory first to notice the usage of the other GPU's memory.

The reason is that accessing memory from a different GPU (via NVlink) is still slower than accessing memory directly from the GPU that is processing it. So to maximize performance we maximize the amount of stuff we store on the GPU first, before we are starting to share data between GPUs. It's kind of similar to the way how out-of-core memory works, where we also try to max out the GPU first before we start using host memory.

When you start using peer-to-peer memory, you will see a blue "overflow" bar in the statistics and the peer-to-peer memory usage in the GPU stats of the viewport.

Also please be aware that NVlink doesn't just magically makes one large memory out of of two smaller ones. There is a bunch of logic in Octane that deals with memory distribution and we have to treat peer-to-peer memory specially.
In theory there is no difference between theory and practice. In practice there is. - Yogi Berra
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Re: How to enable NVLink in OR 2018.1 XB1 ?

Postby Timmaigh! » Mon Dec 24, 2018 8:02 pm

Timmaigh! Mon Dec 24, 2018 8:02 pm
abstrax wrote:The statistics in the viewport don't show the memory that is available by using the other GPU. You will have to run out of memory first to notice the usage of the other GPU's memory.

The reason is that accessing memory from a different GPU (via NVlink) is still slower than accessing memory directly from the GPU that is processing it. So to maximize performance we maximize the amount of stuff we store on the GPU first, before we are starting to share data between GPUs. It's kind of similar to the way how out-of-core memory works, where we also try to max out the GPU first before we start using host memory.

When you start using peer-to-peer memory, you will see a blue "overflow" bar in the statistics and the peer-to-peer memory usage in the GPU stats of the viewport.

Also please be aware that NVlink doesn't just magically makes one large memory out of of two smaller ones. There is a bunch of logic in Octane that deals with memory distribution and we have to treat peer-to-peer memory specially.


I just tried myself, gave myself NVlink under the christmas tree, LOL...and found out its not showing 22GB of VRAM....

Anyway, what does the bolded mean exactly? I dont think its really that important if its magic, or not, how it happens, the most important part is, do we get access to double the VRAM or not? Can we get some more info about what to expect, i mean regarding max available VRAM capacity and speed? If it is slower, by how much exactly? Since its being in use, when needed, am i fine to have it switched on by default and not get any performance penalty then?

The other thing, can be something done with the VRAM taken by the system itself, at last? I mean only 9GB available out of 11, what is this? I remember it used to be far less pre-Windows 10... can you please something do about it? I could accept 500 MB, 1GB maybe...but 2? Why, to what purpose?

Merry Christmas everyone!
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Re: How to enable NVLink in OR 2018.1 XB1 ?

Postby roeland » Wed Dec 26, 2018 9:10 pm

roeland Wed Dec 26, 2018 9:10 pm
Octane still displays the internal GPU memory for each GPU.

If the entire scene fits in the memory of a single GPU, then Octane will just have a copy on each GPU and the peer to peer functionality is not used.

If a scene gets too large, Octane will keep some data on only one GPU and use NVLink. This is indicated with a blue bar graph in the status bar. (out of core usage is indicated with an orange bar graph).
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Re: How to enable NVLink in OR 2018.1 XB1 ?

Postby Timmaigh! » Thu Dec 27, 2018 6:49 pm

Timmaigh! Thu Dec 27, 2018 6:49 pm
Thank you for clarification
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Re: How to enable NVLink in OR 2018.1 XB1 ?

Postby oscartung » Wed Feb 13, 2019 4:18 am

oscartung Wed Feb 13, 2019 4:18 am
I have three cards on my system but I fail to see the option to enable SLI in Nvidia's Control Panel,
anyhelp would be appreciated.
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Re: How to enable NVLink in OR 2018.1 XB1 ?

Postby bepeg4d » Wed Feb 13, 2019 10:21 am

bepeg4d Wed Feb 13, 2019 10:21 am
Have you tried here?
4AE8C06E-1701-44AA-A551-6CC8962D227F.jpeg

ciao Beppe
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Re: How to enable NVLink in OR 2018.1 XB1 ?

Postby linvanchene » Wed Feb 13, 2019 11:35 am

linvanchene Wed Feb 13, 2019 11:35 am
oscartung wrote:I have three cards on my system but I fail to see the option to enable SLI in Nvidia's Control Panel,
anyhelp would be appreciated.


When I tried use one GTX 1080 as display card and two RTX 2080 Ti linked together with a NV Link it was not possible to activate SLI in the Nvidia Control panel.

For using NV Link it seems required that the display is connected to one of the RTX cards that are attached to the NV Link Bridge.
Win 10 Pro 64bit | Rendering: 2 x ASUS GeForce RTX 2080 Ti TURBO | Asus RTX NVLink Bridge 4-Slot | Intel Core i7 5820K | ASUS X99-E WS| 64 GB RAM
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Re: How to enable NVLink in OR 2018.1 XB1 ?

Postby oscartung » Thu Feb 14, 2019 1:59 am

oscartung Thu Feb 14, 2019 1:59 am
linvanchene wrote:
oscartung wrote:I have three cards on my system but I fail to see the option to enable SLI in Nvidia's Control Panel,
anyhelp would be appreciated.


When I tried use one GTX 1080 as display card and two RTX 2080 Ti linked together with a NV Link it was not possible to activate SLI in the Nvidia Control panel.

For using NV Link it seems required that the display is connected to one of the RTX cards that are attached to the NV Link Bridge.


oh that's a a pity, using the card simultaneous for the display and rendering would heavily affect viewport performance
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Re: How to enable NVLink in OR 2018.1 XB1 ?

Postby roeland » Thu Feb 14, 2019 3:07 am

roeland Thu Feb 14, 2019 3:07 am
it seems required that the display is connected …

I think that is correct. You also often have to use specific slots on your motherboard.
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