Bug 499849

Summary: Slightly depressed framerate in Application Dashboard with adaptive sync/VRR turned on
Product: [Plasma] plasmashell Reporter: Shmerl <shtetldik>
Component: Application Dashboard widgetAssignee: Marco Martin <notmart>
Status: REPORTED ---    
Severity: minor CC: ilikefoss, jan.rathmann, kdedev, madness742, nate, niccolo
Priority: LO    
Version First Reported In: 6.2.5   
Target Milestone: 1.0   
Platform: Debian testing   
OS: Linux   
See Also: https://bugs.kde.org/show_bug.cgi?id=494691
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:

Description Shmerl 2025-02-12 01:53:41 UTC
When using fullscreen Application Dashboard, it has erratic and often low framerate.

I noticed it because cursor feels very laggy in it and also shows bad ghosting and trailing. I enabled my display's refresh rate meter (with OCD) and it showed that refresh rate fluctuates a lot there and often drops to 40+ Hz which means that Application Dashboard produces inconsistent and often low framerate. My display has adaptive sync / VRR so it aligns refresh rate to window's framerate when it's a fullscreeen window like video or games or in this case the fullscreen Application Dashboard.

So there must be something wrong with Application Dashboard that it can't sustain a high enough framerate (which also should be preferably constant and match display settings current refresh rate).
Comment 1 Jan Rathmann 2025-02-12 10:57:51 UTC
Can't reproduce on Plasma master, though I don't have a display with adaptive sync/ VRR.

Have you tried enabling the "Show FPS" desktop effect, to see if this also shows that the frame rate is dropping when using the Application Dashboard?

Providing detailed information about your graphics hardware, distro and whether you use the Wayland or the X11 session could also be helpful.
Comment 2 Shmerl 2025-02-12 16:13:38 UTC
I'm using Debian testing, Wayland session.

GPU: AMD Sapphire Nitro RX 7900 XTX
Display: LG UltraGear GP27850-B (180 Hz max, adaptive sync / VRR in the 40 Hz to 180 Hz range).

Some obvervations:

My display settings in KDE set 180 Hz which normal desktop runs at properly.

When enabling fps meter widget in system effects, it forces Application Dashboard to run at 180 fps too and display's OSD confirms that. But without that widget, Application Dashboard runs with erratic framerate which is demonstrated by display's OSD fluctuating and often low refresh rate as in the bug report (as low as 40+ Hz).

So unfortunately FPS widget actually interferes with reproducing of the problem since I suspect it forces an extra window on top of the fullscreen one which makes KWin run things at full desktop setting (180 fps) unlike how it handle Application Dashboard alone.

I hope that helps, but to reproduce it you do need a display with adaptive sync.
Comment 3 Shmerl 2025-02-12 23:27:33 UTC
All that happens when adaptive sync is set to automatic (or always) in display settings. Disabling it (setting to to never) forces 180 Hz all the time in my case so this problem doesn't surface in that scenario (which I think what you are getting in practice too, since your monitor doesn't have VRR support).
Comment 4 Shmerl 2025-02-12 23:32:21 UTC
I see at least two things that can be done to improve the current experience:

1. Make kwin not use adaptive sync with Application Dashboard (may be not the right solution?), this way monitor will run at desktop setting refresh rate no matter what Application Dashboard is doing.
2. Make Application Dashboard itself produce a stable and high framerate instead of erratic and low one, then adaptive sync won't drop monitor refresh rate so low when in it, as it happens now.
Comment 5 Shmerl 2025-02-13 02:44:36 UTC
Just confirm, updated to Plasma 6.3.0 - it still happens in it.
Comment 6 TraceyC 2025-02-18 22:48:13 UTC
Setting the Version string back
Comment 7 Shmerl 2025-02-18 22:49:20 UTC
(In reply to TraceyC from comment #6)
> Setting the Version string back

Not sure why, it happens in 6.3 too.
Comment 8 TraceyC 2025-02-19 16:34:45 UTC
See the field descriptions here for an explanation of why we need the older version (these are linked from the bug fields)
https://bugs.kde.org/page.cgi?id=fields.html
Comment 9 John 2025-02-28 10:57:09 UTC
Could this be related to?:
https://bugs.kde.org/show_bug.cgi?id=500754
While I have a lot of stuttering in Steam games, even for just moving the mouse, I just enabled the alternative application dashboard menu to see if it's laggy or it's stuttering, and it's not for me. It's pretty smooth both for hovering and for searching.
Comment 10 Shmerl 2025-02-28 15:46:39 UTC
(In reply to John from comment #9)
> Could this be related to?:
> https://bugs.kde.org/show_bug.cgi?id=500754

Looks like that bug is specific to Intel GPUs. I'm using AMD.
Comment 11 Shmerl 2025-03-09 01:24:37 UTC
This issue has improved in Plasma 6.3.2 + Qt 6.8.2.

Framerate still has occasional drops in the dashboard, but it's way less frequent and it mostly stays at max display refresh rate now (180 fps for me).
Comment 12 Niccolò Venerandi 2025-10-03 12:17:55 UTC
Is there something specific that causes the framerate drop? If we're unable to reproduce it, it will be hard to work on it, though it's good that it has improved by itself…
Comment 13 Shmerl 2025-10-03 15:11:15 UTC
I assume the dashboard wasn't sustaining full framerate that's equal to monitor's refresh rate and something was wrong with adaptive sync there as well.
Comment 14 Bug Janitor Service 2025-10-18 03:47:12 UTC
🐛🧹 ⚠️ This bug has been in NEEDSINFO status with no change for at least 15 days. Please provide the requested information, then set the bug status to REPORTED. If there is no change for at least 30 days, it will be automatically closed as RESOLVED WORKSFORME.

For more information about our bug triaging procedures, please read https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging.

Thank you for helping us make KDE software even better for everyone!
Comment 15 Shmerl 2025-10-18 23:23:46 UTC
I'm not sure what kind of information is needed for it.
Comment 16 TraceyC 2025-10-20 15:24:45 UTC
Thanks for responding. This just needed to be set to REPORTED, which I've just now done.
Comment 17 madness742 2025-10-27 20:52:38 UTC
*** Bug 511167 has been marked as a duplicate of this bug. ***
Comment 18 madness742 2025-10-27 21:09:59 UTC
(In reply to Niccolò Venerandi from comment #12)
> Is there something specific that causes the framerate drop? 

I can reproduce this by simply setting Adaptive Sync to `Automatic` prior to opening the Application Dashboard. The refresh rate will drop when the cursor isn't moving, and also when moving the cursor around in a predictable way over application icons.

I've found two workarounds:

- Create a Window Rule for Plasmashell to force disable Adaptive Sync.

- Assign "Make Window Fullscreen" to a key (System Settings -> Keyboard -> Shortcuts -> Window Management -> Make Window Fullscreen) and press on that key, while the Application Dashboard is open.

Monitor: LG Ultragear 27GL850
GPU: AMD 7900 XTX Nitro+

Operating System: Fedora Linux 42
KDE Plasma Version: 6.4.5
KDE Frameworks Version: 6.19.0
Qt Version: 6.9.2
Kernel Version: 6.17.4-200.fc42.x86_64 (64-bit)
Graphics Platform: Wayland