I use 'yes | head -n 1000000' for a throughput test, and kitty is about 5x faster than xterm and 1/3 the speed of alacritty (zutty does not appear to be packaged in my OS). It's rather unusual to see something that is held up by terminal rendering (sbcl's build process used to be, and they recommended using xterm for faster builds, so 5x faster than xterm is probably "good enough" there).