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I'm using Ubuntu 20.04 (default desktop install, i.e. with Gnome I suppose) and NVIDIA GeForce RTX 2080 GPU. When the GPU is 100% busy with a background process, some apps start lagging. Namely, those are the apps that use non-OpenGL QT rendering (e.g. Telegram Desktop) or GTK/Gnome/Cairo (Sublime Text, Mozilla Firefox). The other apps like Chrome, Terminal, VS Code, and Slack do not lag. When I changed the rendering backend in Sublime Text from GTK/Gnome/Cairo to OpenGL, it stopped lagging too. The lagging appears as a slow UI (long response for switching tabs and windows or scrolling), and characters do not appear immediately as I type them in.

To reproduce this, you can:

  1. Launch a GPU-intensive application in the background, such as Tensorflow or a crypto miner
  2. Launch an app that uses QT (without OpenGL) or Cairo
  3. Try to use the UI in the app

It seems not to be a problem of long CUDA kernels, as some apps work without lags in this setting.

Is there a configuration option to Xorg/Gnome/QT/GTK/Cairo that can help get rid of the lag?

I submitted a bug to one of the apps https://github.com/telegramdesktop/tdesktop/issues/17091 , but its maintainers suggest fixing the problem in the rendering libraries or the OS instead.

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  • Your machine is busy it gets slow. Do not know of any setting is going to make it less busy.
    – David
    Oct 11 at 11:43
  • @David, but it is fine for some apps, but not the others. So it seems I just need to configure those specific rendering libraries. Oct 11 at 11:57

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