Fixing KWin's performance on old hardware
Quoting: Fixing KWin’s performance on old hardware | Xaver’s blog —
Understanding the issue requires some minimal understanding about how displays work. My earlier post about gaming on Wayland goes into more depth about them and the different presentation modes, but the TL;DR is that most displays today require frames to be sent to it in fixed intervals if you want them to be shown without tearing artifacts.
With the vast majority of displays, that interval is 16.67ms. In order to show everything as smooth as possible, the compositor thus has to render a new frame every 16.67ms as well; it must not miss a single deadline or the user will see stutter as some frames are shown twice and others are skipped.
This problem is not unique to Intel of course, when the deadline is missed, that causes the same stutter on every system. It’s just an often reported issue on old Intel processors because they’re used a lot, because both CPUs and GPUs in them are pretty slow, and laptop manufacturers too often paired them with high resolution screens, requiring the GPU to render for a long time each frame.