As you may have read many times, Gnome 3.34 brings much improved desktop performance. In this article we will describe some of the improvements contributed by Canonical, how the problems were surprising, how they were approached and what other performance work is coming in future.

The thing is in the case of Gnome Shell its biggest performance problems of late were not hot spots at all. They were better characterised as cold spots where it was idle instead of updating the screen smoothly. Such cold spots are only apparent when you look at the real time usage of a program, and in not the CPU or GPU time consumed.

Nice write-up on addressing stuttering and lag.

source: ars