Laptop screen's refresh rate of 60 Hz behaves like 30 Hz

Hi,
I have an Asus M3502QA laptop, which has a screen capable of running at 120 Hz. KDE’s monitor settings offer me the choice of running it at 120 Hz or 60 Hz. At 120 Hz, it works perfectly, the actual FPS is 120 (it looks super smooth & also confirmed by enabling the “Show FPS” Plasma effect and checking the values in the widget). But when I set it to 60 Hz (e.g. when I want to maximize battery life), there’s clearly something wrong: the maximum FPS shown in KDE’s widget is 60, but the actual FPS value is always stuck on 30, and the computer feels sluggish (it’s very noticeable by simply looking at the mouse cursor while it moves).
Any idea how to fix this?
Thanks!

You might try disabling KScreen2 in background startup settings, restarting Plasma, then using xrandr to set rate. e.g. xrandr --output eDP-1 --rate 60, assuming eDP-1 is your laptop’s monitor output name reported by xrandr or Xorg.0.log. Use glxgears to check operation. If this helps, a bug report against Plasma would be in order, if there isn’t one already on file. If xrandr --rate has no apparent impact run from Konsole, try placing the xrandr command in a startup file, such as a new file in /etc/X11/xinit/xinitrc.d/, or in ~/.xinitrc, then restarting X.

Hi, sorry for the late reply. I forgot to mention that I’m using Wayland, and that I have actually never verified the bug exists on X. I’ll verify this and try your solution.

Try testing with “https://testufo.com” (using firefox as native Wayland browser). What does that report with respect to refresh rate? What compositor settings are in use?

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Sorry again for the late reply. I’ll give you guys feedback later today! Thanks!

Okay, your hint helped me fix this! In the compositor settings, I had set “Latency” to “Prefer a lower latency” (I love tinkering with stuff, maybe too much!). Now 60 Hz feels like 60 Hz. Is this a bug I should report, or is it intended (I don’t think so)? Let me remark that the same compositor settings cause no problem at all when running at 120 Hz.