Bug 468280

Summary:	Kwin: Fractional scaling + adaptive sync @ automatic -> freezes when playing full screen videos
Product:	[Plasma] kwin	Reporter:	Simon <simon.adrian>
Component:	wayland-generic	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED WORKSFORME
Severity:	normal	CC:	bartosz1, xaver.hugl
Priority:	NOR
Version First Reported In:	5.27.4
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	Output of journald after last crash, filtered for kwin messages.

Description Simon 2023-04-08 11:14:57 UTC

Created attachment 157953 [details]
Output of journald after last crash, filtered for kwin messages.

SUMMARY
***
I am on a Lenovo X13 Gen 3 AMD running ArchLinux with open source video drivers only.

When I watch a video on, for example, Youtube in full screen mode, the video begins to stutter quite from the beginning and it gets worse when I exit by double clicking. If I go to full screen again or I simply wait too long for exiting, it is too late and a total freeze happens.

With VLC the situation is better, but typically, after like an 1h or so of watching a video, I end up with a freeze too. Going back and forth to full screen seems to cut down the time till the total freeze happens.
***


STEPS TO REPRODUCE
1. Use a browser (tried both Chrome and Firefox)
2. Go to Youtube and start any video
3. Go back and forth to full screen

OBSERVED RESULT
After at most a few seconds the screen will freeze

EXPECTED RESULT
The video should play without any stuttering or screen freezing

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: ArchLinux
KDE Plasma Version: 5.27.4
KDE Frameworks Version: 5.104.0
Qt Version: 5.15.8

The problem persists at least since version 5.27.0, but maybe even since 5.26.0

ADDITIONAL INFORMATION
1) Under Gnome everything works as expected, so I would exclude hardware problems
2) When I use additional external screens, the problem does *not* exist
3) I normally use 150% scaling throughout all my screens. Going back to 100% did not change the situation (I logged out and logged in again to make sure everything is consistent).
4) I found today this report: https://bugs.kde.org/show_bug.cgi?id=466238
where a similar freeze is describe, however, it occurs in this case only if multiple screens are used.
Nonetheless, as suggested in this report, putting KWIN_DRM_NO_DIRECT_SCANOUT=1 into  /etc/environment fixes also my problem.

Comment 1 Simon 2023-04-08 13:10:34 UTC

Seems that I was too early to claim “KWIN_DRM_NO_DIRECT_SCANOUT=1” fixes the problem.

Indeed, the stuttering is gone, but after 1-2 minutes into the video, I got a freeze.

Comment 2 Simon 2023-05-06 12:12:47 UTC

Addendum: Also KWin in X11 is doing fine. So there is some issue with KWin + Wayland

Comment 3 Simon 2023-05-14 08:03:36 UTC

Another update:

1) I wrote that the problem also persists with 100 % scaling. This is, at least now, no longer true. The problem does not exist with normal scaling, but only with fractional scaling.
2) It seems to be related to adaptive sync. I had used "automatic" as option, which allowed normal desktop usage, but made the problems with full screen videos. If I select "Always", my desktop basically freezes (at least, when there are some applications open). Deactivating "adaptive sync" seems to fix my problem. I need to do some more long term tests.

Comment 4 Zamundaaa 2023-05-14 17:27:00 UTC

Please enable drm debug logging (https://invent.kde.org/plasma/kwin/-/wikis/Debugging-DRM-issues), reproduce the freeze and upload the log here

Comment 5 Bug Janitor Service 2023-05-29 03:45:12 UTC

Dear Bug Submitter,

This bug has been in NEEDSINFO status with no change for at least
15 days. Please provide the requested information as soon as
possible and set the bug status as REPORTED. Due to regular bug
tracker maintenance, if the bug is still in NEEDSINFO status with
no change in 30 days the bug will be closed as RESOLVED > WORKSFORME
due to lack of needed information.

For more information about our bug triaging procedures please read the
wiki located here:
https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging

If you have already provided the requested information, please
mark the bug as REPORTED so that the KDE team knows that the bug is
ready to be confirmed.

Thank you for helping us make KDE software even better for everyone!

Comment 6 Bug Janitor Service 2023-06-13 03:45:24 UTC

This bug has been in NEEDSINFO status with no change for at least
30 days. The bug is now closed as RESOLVED > WORKSFORME
due to lack of needed information.

For more information about our bug triaging procedures please read the
wiki located here:
https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging

Thank you for helping us make KDE software even better for everyone!

Comment 7 bartosz1 2024-08-28 15:46:36 UTC

Hello, the same thing happens to me. In my case, it is even when the scalling is set to 100%, on an external display connected to my laptop. The display just loses the input audio/video signal when the refresh rate tries to change. For me it happens with every app that tries to work in a full-screen mode. Turning adaptive sync off helps to prevent this issue from happening.

Comment 8 Zamundaaa 2024-09-05 13:00:39 UTC

When that happens, it's either a display bug (never seen that before) or a driver bug. Please report that to your driver vendor (https://gitlab.freedesktop.org/drm/i915/kernel/-/issues for Intel, https://gitlab.freedesktop.org/drm/amd/-/issues for AMD or https://forums.developer.nvidia.com/c/gpu-graphics/linux for NVidia)