Bug 396551 - Scrolling not smooth without MaxFPS=75 and RefreshRate=75
Summary: Scrolling not smooth without MaxFPS=75 and RefreshRate=75
Status: RESOLVED FIXED
Alias: None
Product: kwin
Classification: Plasma
Component: platform-x11-standalone (other bugs)
Version First Reported In: 5.12.6
Platform: Kubuntu Linux
: NOR minor
Target Milestone: ---
Assignee: KWin default assignee
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2018-07-16 00:40 UTC by Scott Deagan
Modified: 2021-11-06 21:31 UTC (History)
1 user (show)

See Also:
Latest Commit:
Version Fixed/Implemented In:
Sentry Crash Report:


Attachments
xrandr -q output (1.93 KB, text/plain)
2018-07-16 00:40 UTC, Scott Deagan
Details
Requested output of Support Information (6.04 KB, text/plain)
2018-07-16 09:03 UTC, Scott Deagan
Details

Note You need to log in before you can comment on or make changes to this bug.
Description Scott Deagan 2018-07-16 00:40:53 UTC
Created attachment 113958 [details]
xrandr -q output

I have a Lenovo ThinkPad T470 running Kubuntu 18.04. With the default install, moving windows around and scrolling (in Firefox or an Android Virtual Device) was noticeably "jerky" ("micro-stutters" - not sure what else to call it). It was by no means unusable or terrible, but I noticed a significant difference in the "smoothness" compared to my Lenovo ThinkPad T450s.

After spending a lot of time searching for a solution (and if there was indeed a problem) and trying out a load of different tweaks/configs/settings, I finally found a way to make things near "pixel-perfect" smooth:

In ~/.config/kwinrc:

RefreshRate=75
MaxFPS=75

This seems odd as my T470 panel is a 60Hz panel (I have attached the output of xrandr -q). I have tried various other settings, but nothing else results in "near pixel-perfect" smoothness for animations/scrolling.

I understand this is very subjective (i.e. discussing scrolling "smoothness"), but I'm not sure how to quantify such an issue.

As mentioned above, I don't have any such issues on my T450s.
Comment 1 Martin Flöser 2018-07-16 04:13:17 UTC
Please provide output of
qdbus org.kde.KWin /KWin supportInformation
Comment 2 Scott Deagan 2018-07-16 09:03:18 UTC
Created attachment 113959 [details]
Requested output of Support Information

Requested output of Support Information.
Comment 3 Martin Flöser 2018-07-16 15:09:38 UTC
Please try setting compositing to default OpenGL 2.
Comment 4 Scott Deagan 2018-07-17 00:56:45 UTC
Reverting to OpenGL 2 makes not difference - scrolling still exhibits "micro-stutters".

I have found that setting MaxFPS and RefreshRate to 65 also works well (i.e. results in very smooth scrolling).
Comment 5 kde.org 2021-11-06 21:26:59 UTC
This issue report is quite old. Can you please confirm, that it still persists with KDE 5.23?
Comment 6 Scott Deagan 2021-11-06 21:28:49 UTC
(In reply to kde.org from comment #5)
> This issue report is quite old. Can you please confirm, that it still
> persists with KDE 5.23?

This is no longer an issue with KDE 5.23. Will close this ticket.
Comment 7 kde.org 2021-11-06 21:31:02 UTC
User reports issue is fixed