Mientras se carga un archivo más grande quepost_max_size en Symfony, el archivo cargado se asigna en la memoria.

Error fatal: Tamaño de memoria permitido de 150994944 bytes agotado (se intentó asignar 84627994 bytes) en /Aplicaciones/MAMP/htdocs/Symfony/vendor/symfony/src/Symfony/Component/HttpKernel/DataCollector/DataCollector.php en la línea 28

¿Por qué Symfony está tratando de asignar un archivo a la memoria en POST?

1 / php.ini

file_uploads = On
upload_tmp_dir = /Applications/MAMP/tmp/php
upload_max_filesize = 32M
post_max_size = 48M

2 / EL CONTROLADOR

<?php
//AcmeDemoBundle/Controller/DemoController
namespace Acme\DemoBundle\Controller;
use Symfony\Component\HttpFoundation\Request;

class DemoController extends Controller
{

public function createAction(Request $request)
{

    if ($request->getMethod() == 'POST')
    {
        if ($_FILES["file"]["size"] < 3000000 )//3Mb
        {
            if ($_FILES["file"]["error"] > 0)
            {
                echo "Return Code: " . $_FILES["file"]["error"] . "<br />";
            }
            else
            {
                if (empty($_POST) && empty($_FILES) && isset($_SERVER['REQUEST_METHOD']) && strtolower($_SERVER['REQUEST_METHOD']) == 'post')
                {
                    echo "The file is bigger than post_max_size in php.ini.";
                }
                else
                {
                    echo "Size: " . ($_FILES["file"]["size"] / 1024) . " Kb<br />";

                    if (file_exists("upload/" . $_FILES["file"]["name"]))
                    {
                        echo $_FILES["file"]["name"] . " already exists. ";
                    }
                    else
                    {
                        move_uploaded_file($_FILES["file"]["tmp_name"],
                            "upload/" . $_FILES["file"]["name"]);
                        echo "Stored in: " . "upload/" . $_FILES["file"]["name"];
                    }
                }
            }
        }
        else
        {
            echo "Invalid file";
        }

    }

    return $this->container->get('templating')->renderResponse('AcmeDemoBundle:Demo:create.html.twig');

}

3 / LA PLANTILLA

//AcmeDemoBundle/Resources/views/Demo/create.html.twig
{% extends "AcmeDemoBundle::layout.html.twig" %}

{% block content %}

<h1>Upload File</h1>

<form action="#" method="post"
      enctype="multipart/form-data">
    <label name="file">Filename:</label>
    <input type="file" name="file" id="file" />
    <br />
    <input type="submit" name="submit" value="Submit" />
</form>

{% endblock %}