I have two theories at least: 1. modesetting can't deal with hiDPI very well; or 2. compiz/unity7 is falling back to software rendering under the modesetting driver.
Can you please test #2? Just tap the Super key to open the Unity7 dash. Is it translucent or solid coloured? Also, failure to set correct permissions for /dev/dri/* I think is lightdm's problem. So adding lightdm here. ** Also affects: lightdm (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1632165 Title: modesetting driver unbearably slow on intel graphics To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/lightdm/+bug/1632165/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs