Improve ABM time budget handling. #8645

src/serverenvironment.cpp

@@ -384,6 +384,9 @@ void ActiveBlockList::update(std::vector<PlayerSAO*> &active_players,
 	ServerEnvironment
 */
 
+// Random device to seed pseudo random generators.
+static std::random_device seed;
+
 ServerEnvironment::ServerEnvironment(ServerMap *map,
 	ServerScripting *scriptIface, Server *server,
 	const std::string &path_world):
@@ -391,7 +394,8 @@ ServerEnvironment::ServerEnvironment(ServerMap *map,
 	m_map(map),
 	m_script(scriptIface),
 	m_server(server),
-	m_path_world(path_world)
+	m_path_world(path_world),
+	m_rgen(seed())
 {
 	// Determine which database backend to use
 	std::string conf_path = path_world + DIR_DELIM + "world.mt";
@@ -1338,13 +1342,7 @@ void ServerEnvironment::step(float dtime)
 		}
 	}
 
-	if (m_active_block_modifier_interval.step(dtime, m_cache_abm_interval))
+	if (m_active_block_modifier_interval.step(dtime, m_cache_abm_interval)) {
-		do { // breakable
-			if (m_active_block_interval_overload_skip > 0) {
-				ScopeProfiler sp(g_profiler, "SEnv: ABM overload skips");
-				m_active_block_interval_overload_skip--;
-				break;
-			}
 		ScopeProfiler sp(g_profiler, "SEnv: modify in blocks avg per interval", SPT_AVG);
 		TimeTaker timer("modify in active blocks per interval");
 
@@ -1354,31 +1352,46 @@ void ServerEnvironment::step(float dtime)
 		int blocks_scanned = 0;
 		int abms_run = 0;
 		int blocks_cached = 0;
-			for (const v3s16 &p : m_active_blocks.m_abm_list) {
+
+		std::vector<v3s16> output(m_active_blocks.m_abm_list.size());
+
+		// Shuffle the active blocks so that each block gets an equal chance
+		// of having its ABMs run.
+		std::copy(m_active_blocks.m_abm_list.begin(), m_active_blocks.m_abm_list.end(), output.begin());
+		std::shuffle(output.begin(), output.end(), m_rgen);
+
+		int i = 0;
+		// The time budget for ABMs is 20%.
+		u32 max_time_ms = m_cache_abm_interval * 1000 / 5;
+		for (const v3s16 &p : output) {
 			MapBlock *block = m_map->getBlockNoCreateNoEx(p);
 			if (!block)
 				continue;
 
+			i++;
+
 			// Set current time as timestamp
 			block->setTimestampNoChangedFlag(m_game_time);
 
 			/* Handle ActiveBlockModifiers */
 			abmhandler.apply(block, blocks_scanned, abms_run, blocks_cached);
+
+			u32 time_ms = timer.getTimerTime();
+
+			if (time_ms > max_time_ms) {
+				warningstream << "active block modifiers took "
+					  << time_ms << "ms (processed " << i << " of "
+					  << output.size() << " active blocks)" << std::endl;
+				break;
+			}
 		}
 		g_profiler->avg("SEnv: active blocks", m_active_blocks.m_abm_list.size());
 		g_profiler->avg("SEnv: active blocks cached", blocks_cached);
 		g_profiler->avg("SEnv: active blocks scanned for ABMs", blocks_scanned);
 		g_profiler->avg("SEnv: ABMs run", abms_run);
 
-			u32 time_ms = timer.stop(true);
+		timer.stop(true);
-			u32 max_time_ms = 200;
-			if (time_ms > max_time_ms) {
-				warningstream<<"active block modifiers took "
-					<<time_ms<<"ms (longer than "
-					<<max_time_ms<<"ms)"<<std::endl;
-				m_active_block_interval_overload_skip = (time_ms / max_time_ms) + 1;
 	}
-		}while(0);
 
 	/*
 		Step script environment (run global on_step())

src/serverenvironment.h

@@ -26,6 +26,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "server/activeobjectmgr.h"
 #include "util/numeric.h"
 #include <set>
+#include <random>
 
 class IGameDef;
 class ServerMap;
@@ -446,7 +447,6 @@ private:
 	IntervalLimiter m_active_blocks_management_interval;
 	IntervalLimiter m_active_block_modifier_interval;
 	IntervalLimiter m_active_blocks_nodemetadata_interval;
-	int m_active_block_interval_overload_skip = 0;
 	// Time from the beginning of the game in seconds.
 	// Incremented in step().
 	u32 m_game_time = 0;
@@ -470,6 +470,9 @@ private:
 	PlayerDatabase *m_player_database = nullptr;
 	AuthDatabase *m_auth_database = nullptr;
 
+	// Pseudo random generator for shuffling, etc.
+	std::mt19937 m_rgen;
+
 	// Particles
 	IntervalLimiter m_particle_management_interval;
 	std::unordered_map<u32, float> m_particle_spawners;