https://bugs.kde.org/show_bug.cgi?id=518206
Bug ID: 518206
Summary: KWin 6.6 Wayland performance regression: desktop lag,
delayed input, and high CPU usage on Intel integrated
graphics (not present in 6.5.5)
Classification: Plasma
Product: kwin
Version First 6.6.0
Reported In:
Platform: Arch Linux
OS: Linux
Status: REPORTED
Severity: major
Priority: NOR
Component: general
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
After upgrading from KDE Plasma 6.5.5 to 6.6.0, the Wayland session became
noticeably sluggish on a laptop with Intel integrated graphics (no discrete
GPU). The issue persists through 6.6.3. Downgrading only the `kwin` package to
6.5.5-3 while keeping all other Plasma 6.6 components at 6.6.x immediately
resolves the problem.
SYMPTOMS
- Noticeable delay (~0.5s) when opening the application launcher
- Laggy mouse cursor movement during desktop interactions
- Input lag when typing in KRunner
- CPU spikes when interacting with Plasma shell components (System Settings,
lock screen, Spectacle)
- Fan spinning more frequently than on 6.5.5
- General sluggishness across all Plasma shell UI, though native applications
(browsers, terminals) are less affected
REPRODUCTION STEPS
1. Run Plasma 6.6.x on Wayland with an Intel iGPU-only system
2. Observe lag when opening the app launcher, using KRunner, or interacting
with System Settings
3. Downgrade only `kwin` to 6.5.5-3: `sudo pacman -U
/var/cache/pacman/pkg/kwin-6.5.5-3-x86_64.pkg.tar.zst`
4. Log out and back in
5. Observe that all lag is gone
WHAT I EXPECTED
Same smooth, responsive desktop experience as Plasma 6.5.5 on Wayland.
WHAT HAPPENED
Desktop interactions became sluggish with delayed input response and visible
CPU spikes, specifically tied to KWin 6.6.
KEY OBSERVATIONS:
- KWin-specific: Downgrading only `kwin` to 6.5.5 resolves the issue. All other
Plasma components remain at 6.6.x.
- Wayland-only: Logging in to an X11 session does not exhibit the problem.
- Not Flatpak-related: The issue occurs with no Flatpak apps installed or
running. (See related bug #516721, which describes a possibly separate
Flatpak-specific variant.)
- Not configuration-related: The issue occurs on a fresh user account.
- Persists through 6.6.3: Tested on 6.6.0 and confirmed still present as of
6.6.3.
SYSTEM INFORMATION
```
Operating System: Arch Linux
KDE Plasma Version: 6.6.0 (regression present through 6.6.3)
KDE Frameworks Version: 6.23.0
Qt Version: 6.10.2
Kernel Version: 6.18.9-arch1-2 (64-bit)
Graphics Platform: Wayland
Processors: 8 × Intel® Core™ i5-8350U CPU @ 1.70GHz
Memory: 8 GiB of RAM (7.6 GiB usable)
Graphics Processor: Intel® UHD Graphics 620
```
**No discrete GPU present. Intel iGPU is the only graphics adapter.**
OTHER AFFECTED USERS
This regression has been reported independently by multiple users across
different distributions and hardware:
- EndeavourOS, Intel i5-8350U / UHD 620 (this report)
- Fedora 43, Intel Core Ultra 5 125H / Intel Arc iGPU
- KDE Neon, AMD Ryzen (related bug #516721)
- Arch Linux, various hardware (EndeavourOS forum thread:
https://forum.endeavouros.com/t/issues-after-plasma-6-6-update/78216)
- KDE Discuss thread:
https://discuss.kde.org/t/higher-cpu-use-since-plasma-6-6/44565
All reporters confirm the issue is resolved by downgrading KWin to 6.5.x.
SEE ALSO
- Bug #516721 — Performance regression in KWin when using Flatpak (related but
distinct; this bug occurs without Flatpak)
- Bug #516240 — QAnimationDriver fix in 6.6.1 (did not resolve this issue)
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