Mentioned the PHP 7.4 class preloading

Author: javiereguiluz

performance.rst

@@ -17,6 +17,7 @@ Production Server Checklist
 ---------------------------
 
 #. :ref:`Use the OPcache byte code cache <performance-use-opcache>`
+#. :ref:`Use the OPcache class preloading <performance-use-preloading>`
 #. :ref:`Configure OPcache for maximum performance <performance-configure-opcache>`
 #. :ref:`Don't check PHP files timestamps <performance-dont-check-timestamps>`
 #. :ref:`Configure the PHP realpath Cache <performance-configure-realpath-cache>`
@@ -42,6 +43,25 @@ every request. There are some `byte code caches`_ available, but as of PHP
 5.5, PHP comes with `OPcache`_ built-in. For older versions, the most widely
 used byte code cache is `APC`_.
 
+.. _performance-use-preloading:
+
+Use the OPcache class preloading
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. versionadded:: 4.4
+
+    The feature that generates the preloading file was introduced in Symfony 4.4.
+
+Starting from PHP 7.4, OPcache can compile and load classes at start-up and
+make them available to all requests until the server is shut down, improving
+performance significantly. Symfony generates automatically the file with the
+list of classes to preload:
+
+.. code-block:: ini
+
+    ; php.ini
+    opcache.preload=/path/to/project/var/cache/prod/srcApp_KernelProdContainer.preload.php
+
 .. _performance-configure-opcache:
 
 Configure OPcache for Maximum Performance