https://bugs.kde.org/show_bug.cgi?id=526811
Mirek <[email protected]> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEEDSINFO |REPORTED Resolution|WAITINGFORINFO |--- --- Comment #4 from Mirek <[email protected]> --- SUMMARY On an Intel Meteor Lake iGPU (i915), KWin Wayland fails to hold a steady 120 Hz on a 4K 120 Hz external monitor. Scrolling in Firefox and Vivaldi is jerky, and testufo.com shows 115–120 fps with a stutter warning. With KWIN_DRM_NO_AMS=1 (legacy modesetting) it holds a steady 120 fps and scrolling is smooth. STEPS TO REPRODUCE 1. Log into a Plasma Wayland session on an Intel Meteor Lake laptop (i915 driver), with an external 3840x2160 monitor at 120 Hz as the only active display (internal panel disabled). 2. Open https://www.testufo.com in Firefox, or scroll any long webpage in Firefox or Vivaldi. 3. Watch the frame rate and smoothness. OBSERVED RESULT testufo shows 115–120 fps with a stutter warning; scrolling is visibly jerky in both browsers. EXPECTED RESULT A steady 120 fps and smooth scrolling, as with KWIN_DRM_NO_AMS=1, or as on GNOME on the same hardware. SOFTWARE/OS VERSIONS Operating System: Manjaro Linux KDE Plasma Version: 6.7.4 KDE Frameworks Version: 6.29.0 Qt Version: 6.11.2 Kernel Version: 7.2.3-2-MANJARO (64-bit) Graphics Platform: Wayland Processors: 22 × Intel® Core™ Ultra 7 155H Memory: 32 GiB of RAM (30.8 GiB usable) Graphics Processor: Intel® Arc ADDITIONAL INFORMATION Hardware: Intel Meteor Lake-P [Intel Arc Graphics] [8086:7d55], i915 driver, no discrete GPU Distro: Manjaro, kernel 7.2.3-2 Monitor: [model], 3840x2160 @ 120 Hz via [DisplayPort / USB-C / HDMI] Adaptive Sync is not offered in Display settings for this monitor. Findings: - KWIN_DRM_NO_AMS=1: steady 120 fps in testufo, smooth scrolling (current workaround) - KWIN_DRM_DISABLE_TRIPLE_BUFFERING=1: worse, does not reach 120 fps - GPU is not the bottleneck: intel_gpu_top shows the render engine well below full load while stuttering; raising the minimum GPU frequency does not help - Scale factor makes no difference (tested fractional and 200%) - Internal laptop panel was disabled during all tests - No "atomic commit failed" or page flip errors in the user journal in atomic mode - The xe driver (force_probe) gave noticeably smoother scrolling, but caused "TLB invalidation fence timeout" errors with 1–2 second freezes, so it is not usable - GNOME on Ubuntu, same hardware and monitor, scrolls smoothly - The issue reproduces across several distros with Plasma, including 6.7 The attached drm_info.txt was captured with KWIN_DRM_NO_AMS=1 active. -- You are receiving this mail because: You are watching all bug changes.
