Minecraft 19w05a, Minecraft 19w06a
Ubuntu 16.04.5 LTS / Ubuntu 18.04.1 LTS [64 bit]
java version "1.8.0_202" / "11.0.2" 2019-01-15 LTS
Pentium 2.7 Ghz Dual Core
Starting a fresh minecraft server running it with:
/opt/jdk1.8.0_202/bin/java -d64 -Xmx4g -jar server.jar
/opt/jdk-11.0.2/bin/java -Xmx4g -jar server.jar
...where server.jar is one of the following versions:
...yields in a server starting up, generating and loading the world and then waiting for somebody to connect. One of the CPU cores remains on 100% at all times, even after quite some runtime, when somebody is connected or nobody is connected anymore. I had a server running over night and it was still on 100% cpu usage.
I've tested the same scenario with v1.13.2 server.jar and after the initial generation and loading phase, the cpu usage drops first to like 16% and then below 3% and remains there.
I am able to run jvisualvm, if necessary. Since I have not much experience with the tool (and which probings you would need), I could supply you with the necessary data.
However if you'd just test this setup, you should get the same result and analyse this yourself.
Please fix for the next snapshot!