Check if SLI is enabled on Ubuntu

Graphics / Linux Linux
1

Hello,

I am trying to enable SLI on Ubuntu 18.04 (drivers v418) with 2 2080 RTX (and 2 Titan RTX on another computer) and a NVLink component, and check that it is enabled.

I followed this guide (Chapter 28. Configuring SLI and Multi-GPU FrameRendering) and generated a xorg.conf file from nvidia-settings before enabling SLI with nvidia-xconfig --sli=on.

However, after rebooting, I could not find anyway to check if SLI is enabled or not. nvidia-settings does not seem to provide any information about its status, and I could not get any info from dmesg or journalctl.

The only info I could get is that nvlink is enabled. Is there anyway to check it via logs or a command?
I tried to apply the recommendation from the guide but I don’t really understand the check, and I could not detect any difference in lspci -t output before and after enabling SLI.

Thank you for your answer.

Best regards,

2

That should be found in the xorg logs (e.g. /var/log/Xorg.0.log).

3

Thank you, I found the log file.

When checking the Xorg logs, I found the following messages:

[     8.373] (EE) NVIDIA(GPU-0): Failed to find a valid SLI configuration.
[     8.373] (EE) NVIDIA(GPU-0): Invalid SLI configuration 1 of 1:
[     8.373] (EE) NVIDIA(GPU-0): GPUs:
[     8.373] (EE) NVIDIA(GPU-0):     1) NVIDIA GPU at PCI:1:0:0
[     8.373] (EE) NVIDIA(GPU-0):     2) NVIDIA GPU at PCI:2:0:0
[     8.373] (EE) NVIDIA(GPU-0): Errors:
[     8.373] (EE) NVIDIA(GPU-0):     - No video link present
[     8.373] (WW) NVIDIA(GPU-0): Failed to find a valid SLI configuration for the NVIDIA
[     8.373] (WW) NVIDIA(GPU-0):     graphics device PCI:1:0:0. Please see Chapter 29:
[     8.373] (WW) NVIDIA(GPU-0):     Configuring SLI and Multi-GPU FrameRendering in the README
[     8.373] (WW) NVIDIA(GPU-0):     for troubleshooting suggestions.
[     8.373] (EE) NVIDIA(GPU-0): Only one GPU will be used for this X screen.

It seems like the kernel does not detect the nvlink (as it is not listed in lspci at all). On Windows (dual boot machine), the link is properly detected without any issue.

Here is my kernel version: Linux baro-2chan1 5.0.0-20-generic #21~18.04.1-Ubuntu SMP Thu Jun 27 04:04:37 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
And X version: X.Org X Server 1.20.4.

Here is my Xorg.0.log file: http://dpaste.com/3H5DH5W

Is there a minimum kernel version to use with RTX+NVLink or a setting specific to Ubuntu?

Edit: I tried to enable SLI on another computer with exact same software configuration and 2 Titan RTX instead of 2080ti and had an identical result.

4

IMHO, SLI on linux isn’t useful or working properly at all.
At some point, this broke completely with kernel 5.0, don’t know if that has been fixed meanwhile.

5

Hi,
having the exact same problem (same error in the Xorg.0.log file).
running ubuntu 16.04, two titan rtx with nvlink

is there no solution for this?
would be really disappointing if a just bought an nvlink bridge for nothing…

6

Hi,
having the exact same problem (same error in the Xorg.0.log file).
running ubuntu 16.04, two titan rtx with nvlink

is there no solution for this?
would be really disappointing if a just bought an nvlink bridge for nothing…

7

Hi there,
I’m also facing the same problem.

Did anyone of you found a solution?

I look forward to your reply.