MacOS X Yosemite and high WindowServer CPU usage
Since installing Yosemite on my MacBook Pro the whole machine felt sluggish and application felt like 1999. Looking at the Activity Monitor showed that the WindowServer was constantly between 40 and 80%.
Naturally, I started to quit one application after the other, disabled additional 3rd party extensions and more. However, nothing really worked.
Looking further into it and since WindowServer is used by Apple to draw on the screen I looked further into screen settings. To make a long story short, after much trial and error I found that by checking “reducing transparency” in the Accessibility System Preferences I was able to bring the WindowServer CPU usage down to around 10% CPU. It occasionally still spikes up to 50% or higher but for now my Mac is back.
As there are not a lot of posts out there, I hope this helps someone else keeping their sanity 😉