Hello fellow forum scrollers,
i have this issue for quite some time.
My system is an i5-3427U in a Panasonic Toughbook CF-AX2, with Manjaro 20.02 and Kernel 5.9.8, KDE 5.76 and Plasma 5.20.3. So you see, it’s quite a small machine, with not a lot of cpu power, but hey normally it get’s the job done and is mainly use as an office pc.
Everytime, i change the screenbrightness or volume with my fn+x keys, so the function shortcuts, the cpu load spikes to around 50-80% on all 4 threads, and the lag for applying the setting is really high. I looked at htop, and the main process seems to be Xorg.
Is this a known bug, or is there a setting that is probably wrong with me? I mean, it’s not that much of an complicated animation going on there.
Thank you very much in advance, and if i can supply any more useful informations, i would be glad to help 
Regards