Upon switching my mapmaking server from vanilla to spigot, I've noticed a significant increase in CPU usage.
Commands in function seemingly work as expected, however it seems like Functions are overall inefficient.
I've provided a few functions in the attached files which run random commands.
Put the functions folder inside a blank world's data folder (this will kill all entities and make misc modifications to the world, so don't run it on an existing world), start the server with the vanilla server software. Teleport yourself to x=0 y=5 z=0 then run:
Note the average CPU & spikes (a couple minutes should be enough to get an idea), then run the server with Spigot.
In my case, on vanilla I had on average ~20% core usage, with spikes to ~40-50%, whilst using Spigot I had on average ~40% & spikes to >90-100%. In my map, lag essentially increased by a factor of 2 with spigot, but when a lot of functions runs at once the performance violently dwindles even more.