nlmeans filter is crazy-slow

[Dimo]

For a standard 1080p x264 input the nlmeans filter results in ridiculous performance degradation. I'm getting just over 1 fps with the filter and 130+ without the filter.

How to reproduce:

ffmpeg -i in.mkv -filter:v "nlmeans" -c:v hevc_nvenc -preset p7 -rc vbr -cq 24 -c:a copy outputfile.mp4
ffmpeg version N-105185-gce4d459db1-20220105 Copyright (c) 2000-2022 the FFmpeg developers
  built with gcc 11.2.0 (crosstool-NG 1.24.0.498_5075e1f)

It's worth mentioning that I tried the plain non-gpu HEVC codec with no noticeable improvement. Meanwhile, Handbrake is easily pulling off 15fps (which is still quite sad) for the same file but they seem to have their own entirely independent implementation that's not using FFmpeg for filtering.

[Elon Musk]

Beware that default parameters are really slow.