unusually high CPU usage, but only in certain parts of the map

I have a custom map, created with world painter that is about 245 million meters square.

Im running build 2935.

I do run about 40 addons, but the issue that I am experiencing is present even if no addons are running.

While standing near spawn, with only myself logged in, and not performing any actions, the server CPU is around 1%. If i then go to certain other areas, and stand there, doing nothing, the CPU will sometime go up to 75% and remain there.

Ive spent the last few days trying to isolate what could be causing the problem and the only thing that I can think of that differs between the locations that the CPU is low and the locations where the CPU stay high, is the terrain elevation, and slope.

The locations where the CPU remains high are high elevations where the terrain slope is very steep.

I do have some mountain peaks where the terrain reaches built height, with snow capped peaks.

Other than that, I cant figure out why these chunks, when loaded, would cause the server CPU to be working so hard.


The problem didn't surface until the 1.7 release.
I do realize that the dev is new, and there are bound to be bugs.
I'm debating rolling back to 1.6.4 but I would much rather continue to move forward.

The issue is killing my custom dungeon areas though because when a player enters these ' bad areas' the mobs slow to a crawl, and everything else ( block breaks, block places ) ect are all being affected.

Has anyone else seen this particular issue?

It's very hard to replicate I realize. It's easy for me to replicate it on my server, ( since i know what areas are causing the problem ) but I can understand why someone else may have a problem replicating it.

 

There isn't enough information here really to know for sure so anyone replying would be guessing in the dark. If your map is downloadable somewhere and I can reproduce with steps, I could offer a quick analysis.

Some thoughts:
- Does it repro if you kill all the monsters while standing in that area? I know sometimes if you let too many monsters gather at a certain spot (like a mob spawner) it can lag up. Also in 1.7 I noticed some terrain and the monster AI seem to cause them to gather together in certain areas. So could be one theory (as mentioned above a wild guess).
- Is there any redstone involved? For example redstone clock that causes a lighting change repeatedly can cause lag. Or otherwise something that could cause re-lighting repeatedly.
- Corrupt chunks or regions? Could see if problem disappears when removing select region files and letting them automatically re-generate. If doesn't reproduce you could at least narrow down the exact region files involved if not already.

Anyway, as you can see more information is needed. A reproducible case someone could peak into the call stack would more deterministic.

 

All I can suggest is checking for too many entities or too many mobs.