GNOME 3.34's Mutter Lowers Output Lag On X11 To Match Wayland Performance
GNOME has experienced higher output lag on X.Org-based sessions rather than Wayland in some configurations. In particular, the higher output lag on X11 could be experienced when dragging around windows and seeing possible lag. Fortunately, as of today's latest Mutter 3.33 series development code, that lag has been addressed.
Canonical's Daniel van Vugt who has been working on some amazing usability and performance improvements to GNOME ever since Ubuntu switched back to it is responsible for this latest fix. The fix to address this possible output lag corrects the handling of the scheduled frame timing. The corrected behavior ensures the buffer queue isn't overfilled and is just being double-buffered to ensure less visible lag.
The issue has been known for the past seven months but today was finally merged into Mutter for what will end up being part of GNOME 3.34. The output performance now should largely match that of GNOME running on the Wayland-based session.
We've seen some continued performance optimizations already this cycle following the much optimized GNOME 3.32 release while hopefully even more optimizations will make it into 3.34 for better Linux desktop performance.