Arch Linux

Kwin on Wayland is supposed to run as a real time process. If this is not done the user might suffer from input lags like a stuttering mouse cursor in some applications on Plasma Wayland. But Kwin is a compositor on Wayland, all input are handled by this process and as such it should not be in the same scheduling group as the other normal applications. THis is a packaging issue, for details see bug report: https://bugs.kde.org/show_bug.cgi?id=398391

Additional explanation: https://blog.martin-graesslin.com/blog/2017/09/kwinwayland-goes-real-time
Release notes: https://www.kde.org/announcements/plasma-5.12.0.php

Additional info:
* Plasma 5.13.5

$ ps -eL | grep kwin
1616 1616 tty2 00:00:01 kwin_wayland
1616 1620 tty2 00:00:00 kwin_wayla:cs0
1616 1621 tty2 00:00:00 kwin_wa:disk$0
1616 1622 tty2 00:00:00 kwin_wayla:sh0
1616 1623 tty2 00:00:00 kwin_wayla:sh1
1616 1624 tty2 00:00:00 kwin_wayla:sh2
1616 1625 tty2 00:00:00 kwin_wayla:sh3
1616 1626 tty2 00:00:00 kwin_wayla:sh4
1616 1627 tty2 00:00:00 kwin_wayla:sh5
1616 1628 tty2 00:00:00 kwin_wayla:sh6
1616 1629 tty2 00:00:00 kwin_wayla:sh7
1616 1630 tty2 00:00:00 kwin_wayla:sh8
1616 1631 tty2 00:00:00 kwin_wayla:sh9
1616 1632 tty2 00:00:00 kwin_wayla:sh10
1616 1633 tty2 00:00:00 kwin_wayla:sh11
1616 1634 tty2 00:00:00 kwin_way:shlo0
1616 1635 tty2 00:00:00 kwin_way:shlo1
1616 1636 tty2 00:00:00 kwin_way:shlo2
1616 1637 tty2 00:00:00 kwin_way:shlo3
1616 1638 tty2 00:00:00 kwin_way:shlo4
1616 1639 tty2 00:00:00 kwin_way:gdrv0
1616 1703 tty2 00:00:00 kwin_wayland
1679 1679 tty2 00:00:00 org_kde_kwin_xc

$ chrt -p 1616
Derzeitige Scheduling-Vorschrift für PID 1616: SCHED_OTHER
Derzeitige Scheduling-Priorität für PID 1616: 0

$ getcap -v /usr/bin/kwin_wayland
/usr/bin/kwin_wayland

Steps to reproduce:
1.) Run Plasma Wayland
2.) Check kwin_wayland SCHED policy, it is not CAP_SYS_NICE