When I generate a brand new 1.13 world I usually easily get 60+ FPS.
But, as soon as ocean biomes start generating, particularly it seems if I enter the biome or if the biome is in range of spawn chunks, the memory usage starts to spike and the ms/tick rate quickly rises to 1000-3000 or more ms per tick.
The game stops responding to inputs reliably and I usually end up in a 1 FPS or worse situation. While in this situation I've had the game crash twice so far, but unfortunately did not have the crash reporting enabled at the time. I have now turned it on but coincidentally haven't crashed since doing so.
Oddly, I played in Pre-Release 5 on the same computer while coincidentally also opened to LAN playing with my daughter on a world for hours over the course of a couple days doing nothing but exploring oceans for treasures with almost no lag issues at all. But with the release version, the moment any oceans generate I'm in a slide-show.
The console logs errors like:
Can't keep up! Is the server overloaded? Running 12635ms or 252 ticks behind
Quitting to menus and reloading the world is insufficient to clear the issue.
Quitting Minecraft entirely and then reloading the world seems to resolve the problem for a minute or two, but the lag spikes start very quickly if you are in range of an ocean.
I did search for existing issues before creating this, but none seemed to match the Minecraft platform, version, and symptoms properly. Apologies if I missed one.
I don't see a way to close or delete this ticket myself so I'll just comment on it.
I spent a few additional hours today troubleshooting this issue, particularly comparing my Snapshot Profile environment to my Latest Release profile environment and I discovered the Latest Release had view range set to 32 chunks... Unfortunately with all the busyness of the oceans now 32 chunks eats the default 1GB of memory pretty quickly and it seemed to be the cause of the lag spikes.
I tried adjusting the snapshots to 32 chunks and the release profile to 16 chunks and the issue did seem to transfer so I'm pretty confident this is the cause.
I then adjusted my release profile to run with 4GBs memory and it seems to support the 32 chunks just fine. I will look into optimizing my Minecraft settings and apologies for the bug post. :~)
Meanwhile, 1.13 is awesome!