Bug 448473

Summary:	Frame rate varies between 28 and 48 while a maximized window is focused
Product:	[Plasma] kwin	Reporter:	Patrick Silva <bugseforuns>
Component:	input	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED NOT A BUG
Severity:	normal	CC:	nate
Priority:	NOR	Keywords:	wayland-only
Version First Reported In:	5.23.90
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Patrick Silva 2022-01-14 16:05:48 UTC

SUMMARY
According to 'Show fps' effect enabled in 'Desktop Effects' KCM, when my desktop is focused, frame rate is 58.
However, when System Settings is maximized and focused, frame rate is 48, and when Konsole is maximized and focused, frame rate is 28. Furthermore, mouse pointer movement feels laggy. Tried all 'Latency' settings available in Compositor KCM, but nothing changes.

STEPS TO REPRODUCE
1. use Wayland session
2. enable 'Show fps' effect in Desktop Effects KCM
3. observe the frame rate while your desktop is focused, maximized Konsole is focused, maximized System Settings is focused

OBSERVED RESULT
frame rate is lower than normal, laggy mouse pointer movement

EXPECTED RESULT
 in my case, constant 60 fps (refresh rate is 60 Hz in Display Configuration KCM)

SOFTWARE/OS VERSIONS
Operating System: Arch Linux
KDE Plasma Version: 5.23.90
KDE Frameworks Version: 5.90.0
Qt Version: 5.15.2
Kernel Version: 5.16.0-arch1-1 (64-bit)
Graphics Platform: Wayland
Processors: 2 × Intel® Celeron® CPU G1820 @ 2.70GHz
Memory: 7,6 GiB of RAM
Graphics Processor: Mesa DRI Intel® HD Graphics

Comment 1 Patrick Silva 2022-01-14 16:08:09 UTC

journalctl log says:

kwin_wayland[6083]: kwin_libinput: Libinput: event4  - Logitech USB Keyboard: client bug: event processing lagging behind by 22ms, your system is too slow

Comment 2 Nate Graham 2022-01-14 21:37:07 UTC

Input handing is known to be non-ideal, yeah. I think it's being worked on.

Comment 3 Vlad Zahorodnii 2022-01-26 16:17:49 UTC

laggy input: was fixed

lower frame rate: the show fps measures the compositing frame rate, it's not the same as the output refresh rate, if there's nothing to paint, the compositing frame rate will be lower