Why does the nv_open_q process in my system take up too much CPU without running additional processes outside the system?

[Turbolento]

OS: unraid 6.12.8

Graphics card: RTX 3060 Laptop GPU

Open Source Driver: v550.40.07

I will provide more information if necessary.

[Turbolento]

Before installing the Open Source Driver, the CPU usage was below 5%. After installing the Driver, the usage has been around 25%.

[aritger]

That is surprising. open_q was added fairly recently to better parallelize user-space processes opening /dev/nvidia* files, but it should be idle the vast majority of the time.

What else is the system doing when you see this? E.g., do you have an X server running? Or wayland compositor? Or nvidia-persistenced?

An nvidia-bug-report.log might help, too.

[Turbolento]

@aritger Thank you for your answer. After 24 hours, the CPU usage should have returned to the normal range. However, I will continue to observe in the future. If the CPU abnormality occurs again, I will record and upload nvidia-bug-report.log

[xeekworx]

I'm on UNRAID 6.12.10 and I am noticing this going on right now. It's pegging 3 of my logical processors.

[xeekworx]

There shouldn't be anything using this GPU right now; I do not see any apps utilizing it in the GPU stats right now, no one is watching Plex videos where I have it configured to be used for encoding right now.

[xeekworx]

nvidia-bug-report.log.gz
The nvidia-bug-report.log for my system. I actually couldn't kill that process for some reason so I'm about to reboot the system.

[Masses3581]

I could copy&paste everything from @xeekworx. I have the same version of Unraid Server 6.12.10, same NVIDIA driver version 550.67, same problems.... :-( The nv_open_q thread is boosting up my CPU system, normally it should stay quiet.
The only difference i see ist: i am using emby server instead of plex.
nvidia-bug-report.log.gz

I hope this helps maybe to identify the problem source. Thank you for help.

[mtijanic]

As Andy says, this is really surprising, probably a case of some userspace process misbehaving. We'll dig through the attached bug reports, thanks!

In the meantime, could someone please try using the NVreg_EnableNonblockingOpen=0 module param and report back whether it makes the issue go away?

[JsGraaf]

Fixed it for me. For reference, I'm on Fedora 40 with 6.8.10-300.fc40.x86_64 and Nvidia kernel 550.78 with a GTX1650 Max-Q

[amrit1711]

Hi All,
Request you to please trace open calls with bpftrace as per below example.
You can download the latest binary from https://github.com/bpftrace/bpftrace/releases.

bpftrace -e 'kprobe:nvidia_open { printf("[%llu] nvidia_open by %s\n", nsecs, comm); }'

[kbareis]

For folks on Unraid, I think I figured it out. My nv_open_q only pegs 50% CPU when I am on the dashboard. This is likely due to having the GPU widget enabled so I can see process, memory usage, and such. What is funny is as soon as I move to another tab, the process drops back down to almost 0.

[luyufan498]

Same to me, seems that the dashboard is the key ...

[luyufan498]

The nv_open_q uses 50% of 8700K..

switch to the other panel does fix this....

[CorneliusCornbread]

Seeing this happen with Unraid as well, nv_open_q using tons of CPU usage while Plex is idle. Insanely obnoxious, driver version 560.28.03, Unraid 6.12.11