Just a heads up for anyone planning on using this mod for 1.7.10 Servers, this mod causes a huge CPU memory leak, seriously huge. CPU Usage spikes to 95% when idle, tested multiple times. Once the mod was removed, CPU usage went down to 1-3% when idle and 5% with about 20 players on. This was on the most recent 1.7.10 version, haven't tested the 1.8 version.
-- SlenderMiner @ Minecraft Forum

The days of 1.17.10 are over. I think I can close that now.

I may have discovered this problem on a 1.7.10 server.

What causes this bug? Is it a bug that can be avoided on a smaller server, or completely unavoidable and game-breaking?

I'm working on an NBT format that stores the map in smaller segments on the packet rework branch. It might be that updating a single large NBT tag takes a lot of work. Then again, when you're working with a hammer, every problem looks like a nail. I'll check this bug again when I fix #48.

PS. When I ran into the bug, it would only slow down when you were holding the map. Go figure.

How long does it take the server to reach this point, and what configuration makes this bug occur? Did you have a lot of maps/markers/explored area/dimensions? I've been trying to reproduce this bug, with forge 10.13.14.1558-1.7.10-universal and VisualVM's profiling tools, but with one player logged in, the heap has only shrunk over the course of an hour (from ~350Mb, to ~250Mb). CPU usage has stayed around 3%.

Most of the newer issues I never personally verified. We may have to contact SlenderMiner for details.

have you tried having several players on? it could be done in debug mode by running several client apps on one machine.

Unable to reproduce bug.