Public bug reported: [ Impact ]
Fullscreen direct scanout is not used if you enable the hidden experimental VRR feature in Mutter 46. [ Test Plan ] 0. Find a monitor that is VRR capable. 1. Set MUTTER_DEBUG=kms in /etc/environment 2. Enable VRR (TODO: need to relearn all the steps required) 3. Reboot. 4. Log into a Wayland session. 5. Open Google Chrome, start an animation like https://www.vsynctester.com/ and make it full screen (F11). 6. journalctl -f /usr/bin/gnome-shell | grep Post 7. Verify the "Post" messages you see mention direct scan out and not "composite". [ Where problems could occur ] Since the fix affects the runtime decision of whether to allow triple buffering or stay double buffering, the main risk is that triple buffering wouldn't be used in some situation where we would rather have it to maintain a smoother frame rate. [ Other Info ] First reported upstream in: https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1441#note_2062222 We DO NOT recommend enabling the VRR feature anyway because it is still buggy: https://gitlab.gnome.org/GNOME/mutter/-/issues/3419 ** Affects: mutter (Ubuntu) Importance: Low Assignee: Jeremy Bícha (jbicha) Status: Fix Released ** Affects: mutter (Ubuntu Noble) Importance: Low Assignee: Daniel van Vugt (vanvugt) Status: Triaged ** Affects: mutter (Ubuntu Oracular) Importance: Low Assignee: Jeremy Bícha (jbicha) Status: Fix Released ** Tags: noble oracular triple-buffering ** Also affects: mutter (Ubuntu Noble) Importance: Undecided Status: New ** Also affects: mutter (Ubuntu Oracular) Importance: Low Status: Fix Released ** Changed in: mutter (Ubuntu Oracular) Assignee: (unassigned) => Jeremy Bícha (jbicha) ** Changed in: mutter (Ubuntu Oracular) Milestone: None => ubuntu-24.10 ** Changed in: mutter (Ubuntu Noble) Status: New => Triaged ** Changed in: mutter (Ubuntu Noble) Importance: Undecided => Low ** Changed in: mutter (Ubuntu Noble) Assignee: (unassigned) => Daniel van Vugt (vanvugt) ** Changed in: mutter (Ubuntu Noble) Milestone: None => ubuntu-24.04.1 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2070438 Title: Fullscreen direct scanout is not used if you enable the hidden experimental VRR feature in Mutter 46 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/mutter/+bug/2070438/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
