FYI everyone, 1.15 did a number on performance, and uncovered an issue with my old flag set.

A few weeks ago I started tweaking the flags to fix that issue and optimize them even more, and did a lot of beta testing.

We've been stable on the latest set of flags for over a week now, and has shown massive improvement for everyone using them.

These flags are now pretty much required to improve the GC of Java for Minecraft's latest versions.

see https://mcflags.emc.gs

And yes, these flags still work on older versions of MC! And will do even better there. The flaw in the old set did not get hit at all much on the older versions, but the new set will remove all worry, as well as lower GC pause times.

Lots of servers have started switching, as well as some MC Hosts are even helping set them up now.
Some MC Hosts have even told me it is saving them on CPU usage too

Also, from all the GC research again, a lot of people have been evaluating ZGC in newer Java. My recommendation is to avoid ZGC unless you are both: 1) On Java 14, and 2) Have at least 15-20GB of memory given to Xmx.

If you are lower than that on memory, like most servers are, ZGC will end up destroying your performance, even when it says it has low pauses, the pause information is deceptive. If you're curious to know more, ask on Discord or look up "ZGC Allocation Stall"