MeshUpdateQueue: Add a MapBlock cache that minimizes the amount of MapBlock copying done in the main thread

Cache size is configurable by the meshgen_block_cache_size (default 20 MB).

New profiler stats:
- MeshUpdateQueue MapBlock cache hit %
- MeshUpdateQueue MapBlock cache size kB

Removes one type of stutter that was seen on the client when received MapBlocks
were being handled. (the "MeshMakeData::fill" stutter)

Kind of related to at least #5239

Originally preceded by these commits, now includes them:
- Move the mesh generator thread into src/mesh_generator_thread.{cpp,h}
- mesh_generator_thread.cpp: Update code style
- MeshUpdateThread: Modify interface to house a different implementation: Actual functionality will be changed by next commits.
- MeshMakeData: Add fillBlockData() interface (so that caller can fill in stuff from eg. a MapBlock cache)

1 files changed, 6 insertions, 0 deletions

diff --git a/src/mapblock_mesh.h b/src/mapblock_mesh.h
index 916703f3e..25c699e1c 100644
--- a/src/mapblock_mesh.h
+++ b/src/mapblock_mesh.h
@@ -53,6 +53,12 @@ struct MeshMakeData
 			bool use_tangent_vertices = false);
 
 	/*
+		Copy block data manually (to allow optimizations by the caller)
+	*/
+	void fillBlockDataBegin(const v3s16 &blockpos);
+	void fillBlockData(const v3s16 &block_offset, MapNode *data);
+
+	/*
 		Copy central data directly from block, and other data from
 		parent of block.
 	*/