Alexandre Gauthier

I went in and /kill'd all entities, upon return new mobs had spawned in and the problem is indeed gone for now.

Thanks!

Updated to 1.9.0.15 which released today, the problem is still present and somewhat amplified – whenever someone loads a dimension of any kind (on connect or through a portal), now all CPU cores of my server are pegged to 100% for an unreasonably long while, and the tickrate gets really horrible. It eventually stabilizes.

The nether seems to still peg a single core to 100% depending on where you stand inside it.

Also affected on 1.8.1.2 on Ubuntu 18.04 LTS, I've been testing and one single CPU core gets pegged to 100% once someone reaches a specific area of the nether. It will however go back to normal if everyone exits/re-enters. It will also immediately trigger again once players take a few steps in one direction.

Memory remains stable the whole time. Restarting the server while someone is in the nether doesn't seem to help either, as they will immediately trigger the condition again.