Possibly unstable major Ubuntu desktop speedup?

Cross-posting:

http://askubuntu.com/questions/674934/major-desktop-smoothness-improvement-can-someone-duplicate

I just found this while trying to tweak performance in compizconfig – I’m currently running 14.04.3 with all of the available LTS-vivid packages and nvidia-346. The Unity desktop is much, much smoother after toggling off “copy to texture” in compizconfig during a session. There don’t seem to be any performance gains from starting up with it turned off; it has to be toggled mid-session.

Did some more testing and it turns out that when the desktop is in this state, hotplugging displays causes the session to crash back out to the login screen. So it’s not as usable as I hoped in all cases, but this is still really weird.

Can anyone duplicate this? Devs, any idea what might be going on? I know compiz is kind of a mess at this point, but curious. Super+W to move all windows is much, much faster now, and running something compiz-intensive like Google Hangouts no longer slows down the rest of the display when you have CPU+GPU to spare.

This also fixed an issue where Chrome would never report 60fps for streaming video (when I had the FPS meter open from dev tools) – it used to top out at 40. Basically compiz no longer feels nearly as poorly-optimized as I always thought it was.

But I can’t seem to “automatically” get this effect to kick in by writing a bash file that automatically enables and disables the copytex plugin in dconf at login; I have to do it via compizconfig. And there’s still the issue where hotplugging monitors no longer works after having done this. I don’t know if this means that this bottleneck was always enabled on purpose for stability, or what …

It also doesn’t seem to break vsync (unredirect still does though) or negatively impact any other compositor functionality.