<?php

use PDO;
use Workerman\Worker;
require_once 'Workerman/Autoloader.php';

$w = new Worker();
$w->onWorkerStart = function(){
    echo memory_get_usage()."\n";
    $set = Config::getItem('db');
    $pdo = new PDO(
        $set,
        $set,
        $set,

    );
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $stmt = $pdo->prepare("SELECT * FROM orders", );
    $stmt->execute(null);
    $stmt->setFetchMode(PDO::FETCH_ASSOC);
    $data = $stmt->fetchAll();
    $stmt = null;
    echo memory_get_usage()."\n";
    unset($data);
    echo memory_get_usage()."\n";
};

Worker::runAll();開(kāi)啟服務(wù)前，通過(guò)php a.php status查看進(jìn)程的占用內(nèi)存是4M
查詢了數(shù)據(jù)庫(kù)，然后把結(jié)果變量unset了，通過(guò)memory_get_usage()查看內(nèi)存是被釋放了，但是再次php a.php status查看進(jìn)程的占用內(nèi)存是72M
到此我有個(gè)疑問(wèn)，為什么進(jìn)程的內(nèi)存沒(méi)有被釋放？
?