Unexpected Performance differences when application/desktop refresh rate don't match

[romangg]

In GitLab by @ms178 on Apr 13, 2022, 03:08

Split out from https://gitlab.com/kwinft/kdisplay/-/issues/18, I can get reliably 5-7% beter performance with 120 Hz within the application and on the desktop. By default, the desktop is 165 Hz and the (CPU-limited) game is limited to 120 Hz. The resolution is 1440p for both. But I am not sure if this is a problem of KDisplay.

I would expect that there should be no performance difference, as the application is run at 120 Hz regardless of the desktop refresh rate.

This is on X11, GPU is AMD Vega 56.