Add count based unload limit for mapblocks

minetest.conf.example

@@ -94,6 +94,9 @@
 #random_input = false
 #    Timeout for client to remove unused map data from memory
 #client_unload_unused_data_timeout = 600
+#    Maximum number of mapblocks for client to be kept in memory
+#    Set to -1 for unlimited amount
+#client_mapblock_limit = 1000
 #    Whether to fog out the end of the visible area
 #enable_fog = true
 #    Whether to show the client debug info (has the same effect as hitting F5)

src/client.cpp

@@ -421,8 +421,9 @@ void Client::step(float dtime)
 		ScopeProfiler sp(g_profiler, "Client: map timer and unload");
 		std::vector<v3s16> deleted_blocks;
 		m_env.getMap().timerUpdate(map_timer_and_unload_dtime,
-				g_settings->getFloat("client_unload_unused_data_timeout"),
-				&deleted_blocks);
+			g_settings->getFloat("client_unload_unused_data_timeout"),
+			g_settings->getS32("client_mapblock_limit"),
+			&deleted_blocks);
 
 		/*
 			Send info to server

src/defaultsettings.cpp

@@ -104,6 +104,7 @@ void set_default_settings(Settings *settings)
 	settings->setDefault("address", "");
 	settings->setDefault("random_input", "false");
 	settings->setDefault("client_unload_unused_data_timeout", "600");
+	settings->setDefault("client_mapblock_limit", "1000");
 	settings->setDefault("enable_fog", "true");
 	settings->setDefault("fov", "72");
 	settings->setDefault("view_bobbing", "true");

src/map.cpp

@@ -43,6 +43,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "database-dummy.h"
 #include "database-sqlite3.h"
 #include <deque>
+#include <queue>
 #if USE_LEVELDB
 #include "database-leveldb.h"
 #endif
@@ -1399,10 +1400,25 @@ bool Map::getDayNightDiff(v3s16 blockpos)
 	return false;
 }
 
+struct TimeOrderedMapBlock {
+	MapSector *sect;
+	MapBlock *block;
+
+	TimeOrderedMapBlock(MapSector *sect, MapBlock *block) :
+		sect(sect),
+		block(block)
+	{}
+
+	bool operator<(const TimeOrderedMapBlock &b) const
+	{
+		return block->getUsageTimer() < b.block->getUsageTimer();
+	};
+};
+
 /*
 	Updates usage timers
 */
-void Map::timerUpdate(float dtime, float unload_timeout,
+void Map::timerUpdate(float dtime, float unload_timeout, u32 max_loaded_blocks,
 		std::vector<v3s16> *unloaded_blocks)
 {
 	bool save_before_unloading = (mapType() == MAPTYPE_SERVER);
@@ -1416,48 +1432,108 @@ void Map::timerUpdate(float dtime, float unload_timeout,
 	u32 block_count_all = 0;
 
 	beginSave();
-	for(std::map<v2s16, MapSector*>::iterator si = m_sectors.begin();
-		si != m_sectors.end(); ++si) {
-		MapSector *sector = si->second;
 
-		bool all_blocks_deleted = true;
+	// If there is no practical limit, we spare creation of mapblock_queue
+	if (max_loaded_blocks == (u32)-1) {
+		for (std::map<v2s16, MapSector*>::iterator si = m_sectors.begin();
+				si != m_sectors.end(); ++si) {
+			MapSector *sector = si->second;
 
-		MapBlockVect blocks;
-		sector->getBlocks(blocks);
+			bool all_blocks_deleted = true;
 
-		for(MapBlockVect::iterator i = blocks.begin();
-				i != blocks.end(); ++i) {
-			MapBlock *block = (*i);
+			MapBlockVect blocks;
+			sector->getBlocks(blocks);
 
-			block->incrementUsageTimer(dtime);
+			for (MapBlockVect::iterator i = blocks.begin();
+					i != blocks.end(); ++i) {
+				MapBlock *block = (*i);
 
-			if(block->refGet() == 0 && block->getUsageTimer() > unload_timeout) {
-				v3s16 p = block->getPos();
+				block->incrementUsageTimer(dtime);
 
-				// Save if modified
-				if (block->getModified() != MOD_STATE_CLEAN && save_before_unloading) {
-					modprofiler.add(block->getModifiedReasonString(), 1);
-					if (!saveBlock(block))
-						continue;
-					saved_blocks_count++;
+				if (block->refGet() == 0
+						&& block->getUsageTimer() > unload_timeout) {
+					v3s16 p = block->getPos();
+
+					// Save if modified
+					if (block->getModified() != MOD_STATE_CLEAN
+							&& save_before_unloading) {
+						modprofiler.add(block->getModifiedReasonString(), 1);
+						if (!saveBlock(block))
+							continue;
+						saved_blocks_count++;
+					}
+
+					// Delete from memory
+					sector->deleteBlock(block);
+
+					if (unloaded_blocks)
+						unloaded_blocks->push_back(p);
+
+					deleted_blocks_count++;
+				} else {
+					all_blocks_deleted = false;
+					block_count_all++;
 				}
-
-				// Delete from memory
-				sector->deleteBlock(block);
-
-				if(unloaded_blocks)
-					unloaded_blocks->push_back(p);
-
-				deleted_blocks_count++;
 			}
-			else {
-				all_blocks_deleted = false;
-				block_count_all++;
+
+			if (all_blocks_deleted) {
+				sector_deletion_queue.push_back(si->first);
 			}
 		}
+	} else {
+		std::priority_queue<TimeOrderedMapBlock> mapblock_queue;
+		for (std::map<v2s16, MapSector*>::iterator si = m_sectors.begin();
+				si != m_sectors.end(); ++si) {
+			MapSector *sector = si->second;
 
-		if(all_blocks_deleted) {
-			sector_deletion_queue.push_back(si->first);
+			MapBlockVect blocks;
+			sector->getBlocks(blocks);
+
+			for(MapBlockVect::iterator i = blocks.begin();
+					i != blocks.end(); ++i) {
+				MapBlock *block = (*i);
+
+				block->incrementUsageTimer(dtime);
+				mapblock_queue.push(TimeOrderedMapBlock(sector, block));
+			}
+		}
+		block_count_all = mapblock_queue.size();
+		// Delete old blocks, and blocks over the limit from the memory
+		while (mapblock_queue.size() > max_loaded_blocks
+				|| mapblock_queue.top().block->getUsageTimer() > unload_timeout) {
+			TimeOrderedMapBlock b = mapblock_queue.top();
+			mapblock_queue.pop();
+
+			MapBlock *block = b.block;
+
+			if (block->refGet() != 0)
+				continue;
+
+			v3s16 p = block->getPos();
+
+			// Save if modified
+			if (block->getModified() != MOD_STATE_CLEAN && save_before_unloading) {
+				modprofiler.add(block->getModifiedReasonString(), 1);
+				if (!saveBlock(block))
+					continue;
+				saved_blocks_count++;
+			}
+
+			// Delete from memory
+			b.sect->deleteBlock(block);
+
+			if (unloaded_blocks)
+				unloaded_blocks->push_back(p);
+
+			deleted_blocks_count++;
+			block_count_all--;
+		}
+		// Delete empty sectors
+		for (std::map<v2s16, MapSector*>::iterator si = m_sectors.begin();
+			si != m_sectors.end(); ++si) {
+			if (si->second->empty()) {
+				sector_deletion_queue.push_back(si->first);
+			}
 		}
 	}
 	endSave();
@@ -1484,7 +1560,7 @@ void Map::timerUpdate(float dtime, float unload_timeout,
 
 void Map::unloadUnreferencedBlocks(std::vector<v3s16> *unloaded_blocks)
 {
-	timerUpdate(0.0, -1.0, unloaded_blocks);
+	timerUpdate(0.0, -1.0, 0, unloaded_blocks);
 }
 
 void Map::deleteSectors(std::vector<v2s16> &sectorList)

src/map.h

@@ -277,7 +277,7 @@ public:
 		Updates usage timers and unloads unused blocks and sectors.
 		Saves modified blocks before unloading on MAPTYPE_SERVER.
 	*/
-	void timerUpdate(float dtime, float unload_timeout,
+	void timerUpdate(float dtime, float unload_timeout, u32 max_loaded_blocks,
 			std::vector<v3s16> *unloaded_blocks=NULL);
 
 	/*

src/mapsector.cpp

@@ -142,6 +142,11 @@ void MapSector::getBlocks(MapBlockVect &dest)
 	}
 }
 
+bool MapSector::empty()
+{
+	return m_blocks.empty();
+}
+
 /*
 	ServerMapSector
 */

src/mapsector.h

@@ -63,6 +63,8 @@ public:
 
 	void getBlocks(MapBlockVect &dest);
 
+	bool empty();
+
 	// Always false at the moment, because sector contains no metadata.
 	bool differs_from_disk;
 

src/server.cpp

@@ -594,7 +594,8 @@ void Server::AsyncRunStep(bool initial_step)
 		// Run Map's timers and unload unused data
 		ScopeProfiler sp(g_profiler, "Server: map timer and unload");
 		m_env->getMap().timerUpdate(map_timer_and_unload_dtime,
-				g_settings->getFloat("server_unload_unused_data_timeout"));
+			g_settings->getFloat("server_unload_unused_data_timeout"),
+			(u32)-1);
 	}
 
 	/*