AsyncWorker now manually triggers GC at the end of each task run, similar to the main thread

this avoids costly GC runs during hot code.

src/GarbageCollectorManager.php

@@ -0,0 +1,102 @@
+<?php
+
+/*
+ *
+ *  ____            _        _   __  __ _                  __  __ ____
+ * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
+ * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
+ * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
+ * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * @author PocketMine Team
+ * @link http://www.pocketmine.net/
+ *
+ *
+ */
+
+declare(strict_types=1);
+
+namespace pocketmine;
+
+use pocketmine\timings\TimingsHandler;
+use function gc_collect_cycles;
+use function gc_disable;
+use function gc_status;
+use function hrtime;
+use function max;
+use function min;
+use function number_format;
+
+/**
+ * Allows threads to manually trigger the cyclic garbage collector using a threshold like PHP's own garbage collector,
+ * but triggered at a time that suits the thread instead of in random code pathways.
+ *
+ * The GC trigger behaviour in this class was adapted from Zend/zend_gc.c as of PHP 8.3.14.
+ */
+final class GarbageCollectorManager{
+	//TODO: These values could be adjusted to better suit PM, but for now we just want to mirror PHP GC to minimize
+	//behavioural changes.
+	private const GC_THRESHOLD_TRIGGER = 100;
+	private const GC_THRESHOLD_MAX = 1_000_000_000;
+	private const GC_THRESHOLD_DEFAULT = 10_001;
+	private const GC_THRESHOLD_STEP = 10_000;
+
+	private int $threshold = self::GC_THRESHOLD_DEFAULT;
+	private int $collectionTimeTotalNs = 0;
+
+	private \Logger $logger;
+	private TimingsHandler $timings;
+
+	public function __construct(
+		\Logger $logger,
+	){
+		gc_disable();
+		$this->logger = new \PrefixedLogger($logger, "Cyclic Garbage Collector");
+		$this->timings = new TimingsHandler("Cyclic Garbage Collector");
+	}
+
+	private function adjustGcThreshold(int $cyclesCollected, int $rootsAfterGC) : void{
+		//TODO Very simple heuristic for dynamic GC buffer resizing:
+		//If there are "too few" collections, increase the collection threshold
+		//by a fixed step
+		//Adapted from zend_gc.c/gc_adjust_threshold() as of PHP 8.3.14
+		if($cyclesCollected < self::GC_THRESHOLD_TRIGGER || $rootsAfterGC >= $this->threshold){
+			$this->threshold = min(self::GC_THRESHOLD_MAX, $this->threshold + self::GC_THRESHOLD_STEP);
+		}elseif($this->threshold > self::GC_THRESHOLD_DEFAULT){
+			$this->threshold = max(self::GC_THRESHOLD_DEFAULT, $this->threshold - self::GC_THRESHOLD_STEP);
+		}
+	}
+
+	public function getThreshold() : int{ return $this->threshold; }
+
+	public function getCollectionTimeTotalNs() : int{ return $this->collectionTimeTotalNs; }
+
+	public function maybeCollectCycles() : int{
+		$rootsBefore = gc_status()["roots"];
+		if($rootsBefore < $this->threshold){
+			return 0;
+		}
+
+		$this->timings->startTiming();
+
+		$start = hrtime(true);
+		$cycles = gc_collect_cycles();
+		$end = hrtime(true);
+
+		$rootsAfter = gc_status()["roots"];
+		$this->adjustGcThreshold($cycles, $rootsAfter);
+
+		$this->timings->stopTiming();
+
+		$time = $end - $start;
+		$this->collectionTimeTotalNs += $time;
+		$this->logger->debug("gc_collect_cycles: " . number_format($time) . " ns ($rootsBefore -> $rootsAfter roots, $cycles cycles collected) - total GC time: " . number_format($this->collectionTimeTotalNs) . " ns");
+
+		return $cycles;
+	}
+}