So, I've just updated my server to 1.4, and now the lag is insane! With the same amount of players online during 1.2.13-16, it was only a max of 40% server load, and now it doubled! Can somebody help me resolve this issue, thank you. If you want details on what could be causing it: https://timings.pmmp.io/?url=p/h2hZXZRvgb
It's not immediately obvious what the problem is - do you have a timings report from before the update to compare?
in 1.2.13, the lag was mainly caused by plugins, but I cleaned it up, so now the issue is in entities, chunks, do ticks, whatever those are.