[Help] Mapgen causes OOM crashes [mod] [snow]

[Hybrid Dog]

The snow mod's mapgen somehow takes too much memory resulting in crashes.
l didn't experience one yet, but someone reported crashes:
https://github.com/Splizard/minetest-mod-snow/issues/22

l couldn't figure out the reason for the memory overfilling yet, please help me.

Here's the mapgen code:
https://github.com/Splizard/minetest-mo ... 6.lua#L175

[paramat]

There are 2 noise optimisations that can be done:
1. Don't recreate noise objects in every mapchunk.
2. Use the new noise buffers in 'get perlin map'.
See this mod for code example https://github.com/paramat/stability/blob/master/init.lua

[Hybrid Dog]

There are 2 noise optimisations that can be done:
1. Don't recreate noise objects in every mapchunk.

Done, thanks.

2. Use the new noise buffers in 'get perlin map'.

What is the difference between putting the noise values into an existing table and storing them in a new table?
https://github.com/minetest/minetest/co ... 769b65R316

[paramat]

The Lua tables that store noise values are big, especially for 3D noise, and garbage collection is slow, creating new tables makes unnecessary duplicate tables build up in number. So a big reduction in memory use.

[Hybrid Dog]

If l use a buffer localized outside the on_generated and a bit map becomes generated but then no more mapgen happens because the players don't load new mapchunks, does the garbage collector remove the buffer because it's unused or does it keep it until shutdown?

[paramat]

No idea, hmmmm might know.

[qwertymine3]

If l use a buffer localized outside the on_generated and a bit map becomes generated but then no more mapgen happens because the players don't load new mapchunks, does the garbage collector remove the buffer because it's unused or does it keep it until shutdown?

You mean like this?

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Code: Select all

local buffer = {}
minetest.register_on_generated(function()
    --Stuff
end)


It can't be freed as it can be accessed the next time the function is called.

[Hybrid Dog]

If somewhere it is marked as weak it (e.g. if the buffer table is stored in a weak table) can be collected, can't it?
And how much memory does buffer use?

[qwertymine3]

If somewhere it is marked as weak it (e.g. if the buffer table is stored in a weak table) can be collected, can't it?
And how much memory does buffer use?

IDK precisely, it would depend on how large you are making the table (minp/maxp or emin/emax).
I made a quick script which created and stored a table of size 112^3 (emin/emax) and called collectgarbage("count");
it reported ~33mb

[Hybrid Dog]

Obviously using noise buffers didn't fix the crash.