Recently I noticed many occurrences of 'unable to fork' errors. I watch the top command for a while, suspecting out of memory issue, but it doesn't look that way.
'ps' command surprisingly shows there are 30k+ processes of nv_queue.
 

-- truncated --
32757 ?        S      0:00 [nv_queue]
32758 ?        S      0:00 [nv_queue]
32759 ?        S      0:00 [nv_queue]
32760 ?        S      0:00 [nv_queue]
32761 ?        S      0:00 [nv_queue]
32762 ?        S      0:00 [nv_queue]
32763 ?        S      0:00 [nv_queue]
32764 ?        S      0:00 [nv_queue]
32765 ?        S      0:00 [nv_queue]
32766 ?        S      0:00 [nv_queue]
32767 ?        S      0:00 [nv_queue]

# ps ax | grep nv_queue | wc -l
31198

This might come from nvidia driver. I have been using the nvidia build for a long time but the only different thing I do recently is the command

nvidia-smi -pm 1

to enable the persistence mode. Without this command, my graphics card (1080Ti) would always at 55W power when idle. With this command, it's down to 9-12W.

Does anyone encounter this issue?
I believe the very large numbers of nv_queue processes here has rendered the system unstable, casuing many other important processes fail to execute due to out of resources.
 

Best bet is to post this on the Nvidia plugin support thread.

Done reposted there. I will delete this post shortly. Thanks @johnnie.black!