FFIopt optimizes access to large amounts of data via the Lua API and reduces Lua memory footprint.

License: LGPL

Description

Lua API methods that transmit large amount of data (VoxelManip:get_data, PerlinNoiseMap:get3dMap_flat) copies data from C++ structures to Lua tables. This copy is quite slow and consumes a lot of Lua memory. FFIopt replaces this copy by a direct access from Lua to C++ data using FFI library. The engine has to be patched to expose some C++ pointers to Lua API. If engine correctly patched, FFIopt hacks VoxelManip and PerlinNoiseMap to use FFI rather than Lua tables.

Result is :

• Faster data retreiving and storing ;
• Slower table access (essencially due to use of metatable avoiding mods code change) ;
• Lower Lua memory footprint (avoiding many OOM errors) ;

How to use it

• Use LuaJIT.
• Patch the engine to add VoxelManip:get_data_ptr, PerlinNoiseMap:get_result_size and PerlinNoiseMap:get_result_ptr methods to the API.
• Install and enable ffiopt mod. On starting Minetest, ffiopt will tell if it is able to optimise voxel manips and perlin noise.
• Nothing to change in mods code.

A successful log example:

2019-04-17 09:58:53: ACTION[Main]: [ffiopt] Using LUAJIT (version LuaJIT 2.0.3).
2019-04-17 09:58:53: ACTION[Main]: [ffiopt] FFI library loaded.
2019-04-17 16:19:44: ACTION[Server]: [ffiopt] PerlinMap can be optimized.
2019-04-17 16:19:44: ACTION[Server]: [ffiopt] VoxelManip can be optimized.