CPU usage is too high when clone device by v4l2loopback

[trungthanhnguyen0502]

CPU usage is too high when clone device by v4l2loopback

[umlaeute]

hmm, well.
the high CPU load you see is obviously in user-space (the green bar), which is GStreamer.
the load in kernel-space (the red bar), which is where you would see anything done by v4l2loopback, seems to be pretty constant.

so i conclude that the v4l2loopback is not doing any excessive work, but instead GStreamer is.
(it could still be a problem with v4l2loopback that makes GStreamer burn your CPU cycles).

so, if I were you, i would do some analysis where GStreamer is spending its time (and see whether something can be done on the v4l2loopback side of things)

[trungthanhnguyen0502]

I tried some analysis with simple gstreamer command. When I run
gst-launch-1.0 v4l2src device=/dev/video0 ! videoconvert ! appsink
CPU usage is 17%.

But when I replace appsink with v4l2sink (to a virtual device created by v4l2loopback). CPU usage is 60%.

[chrisiberg]

I think your problem hast to do with missing DMA support, or am I wrong? @umlaeute
#501

[sanbrother]

I think your problem hast to do with missing DMA support, or am I wrong? @umlaeute #501

Will copy without DMA consume a lot of CPU? mmap still costs high CPU usage?

[angeelalg]

• kernel version: 5.10.104-tegra
• Distribution (+version): Ubuntu 20.04.5 LTS
• Jetson xavier nx: JetPack 5.0.2.
• Deepstream and Gstreamer version are 6.1.1 and 1.16.3.

Hello @trungthanhnguyen0502 , good morning.

How did you get v4l2loopback working for you? I'm trying to get my Jetson NX to work, with the same kernel version and it's impossible. I keep getting this error when running modprobe v4l2loopback:
modprobe: ERROR: could not insert 'v4l2loopback': Operation not permitted