GarbageCollectorManager.php

<?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;
 
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,
        ?TimingsHandler $parentTimings,
    ){
        gc_disable();
        $this->logger = new \PrefixedLogger($logger, "Cyclic Garbage Collector");
        $this->timings = new TimingsHandler("Cyclic Garbage Collector", $parentTimings);
    }
 
    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;
    }
}