| Summary: | Plasma desktop unusable due to stuttering with compositing enabled on VRR display with gsync enabled | ||
|---|---|---|---|
| Product: | [Plasma] kwin | Reporter: | Eduard <e.bachmakov> |
| Component: | general | Assignee: | KWin default assignee <kwin-bugs-null> |
| Status: | RESOLVED UNMAINTAINED | ||
| Severity: | normal | CC: | nate, xaver.hugl |
| Priority: | NOR | ||
| Version: | 5.23.3 | ||
| Target Milestone: | --- | ||
| Platform: | Other | ||
| OS: | Linux | ||
| Latest Commit: | Version Fixed In: | ||
| Attachments: |
perf at 145Hz for 10s on kwin_x11 when gsync-enabled
perf at 145Hz for 10s on kwin_x11 when gsync-disabled |
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Created attachment 144214 [details]
perf at 145Hz for 10s on kwin_x11 when gsync-disabled
I forgot to mention: There's nothing obvious in the logs for kernel, X, krunner, kwin, xsession, etc. But one of the symptoms becomes visible once gsync is enabled: You start seeing entries like
(EE) event3 - DELL Dell USB Entry Keyboard: client bug: event processing lagging behind by 31ms, your system is too slow
for mouse and keyboard despite <5% cpu utilization per core.
This bug was reported against an outdated version of KWin. We have made many changes since the. If the issue persists in newer versions can you reopen the bug report updating the version number. |
Created attachment 144213 [details] perf at 145Hz for 10s on kwin_x11 when gsync-enabled SUMMARY On my single-monitor x11 setup, enabling (a.k.a. "not disabling") gsync in the nvidia-settings causes everything to stutter. This is new since my distro upgrade (see versions below). Happens both logged-in and when sddm is running. It gives the impression that "processing speed" is coupled with the refresh rate. For example, with an empty desktop/no visual movement, triggering krunner takes multiple seconds ... every time. When I trigger it while quickly dragging a window (thus raising the VRR) it happens ~instantly. (It's almost as if it takes a fixed number of frames to show it.) When disabling gsync or compositing, fps is at a locked 144 and no problems occur. This bug sounds somewhat overlapping with #445330 but they explicitly say "x11 is fine" and don't mention VRR. STEPS TO REPRODUCE 1. Have plasma5 desktop running on X11 2. Open nvidia-settings 3. Toggle "Allow G-SYNC/G-SYNC Compatible" from off to on OBSERVED RESULT 1. FPS counter (built into the display itself) unlocks from 144 to a variable number roughly proportional to amount of movement on screen, as low as 1 FPS. 2. During "low FPS times" everything stutters, there are large delays (e.g. krunner or kickoff) EXPECTED RESULT 1. either locked max fps (windows does this) 2. or instant fps scaling without any delays (phones do that I believe) SOFTWARE/OS VERSIONS KDE Plasma Version: 5.23.3 (prev: 5.21.5) KDE Frameworks Version: 5.87.0 (prev: 5.81.0) Qt Version: 5.15.3 (prev: 5.15.2) ADDITIONAL INFORMATION Kernel: 5.15.4 (prev: same) Distro: NixOS 21.11.333896.a640d8394f3 (prev: 21.05) Nvidia driver: 495.44 (prev: 470.63.01) I was curious as to how kwin is handling this internally so peeked at it a bit, see attachments. [gsync-on variant seems to eat quite a bit more cycles and spend a lot of time within destructors?]