Note and link to Logging API

In the Performance section, not only the direct configuration of the core should be taken into account, but at least measures for optimizing logging via API should be pointed out.

Documentation/ApiOverview/ErrorAndExceptionHandling/Examples/Index.rst

@@ -134,6 +134,13 @@ In :file:`config/system/settings.php` or :file:`config/system/additional.php`:
 
    $GLOBALS['TYPO3_CONF_VARS'] = array_replace_recursive($GLOBALS['TYPO3_CONF_VARS'], $changeSettings);
 
+..  note::
+    PHP warnings, among other things, are added to the TYPO3 log via 
+    the [Writer configuration](https://docs.typo3.org/permalink/t3coreapi:logging-configuration-writer) of Logging API. 
+    In production or from a performance perspective, you may not want this. 
+    The default value is :php:`\Psr\Log\LogLevel::WARNING`. 
+    Depending on requirements, the loglevel can be increased to :PHP:`\Psr\Log\LogLevel::ERROR`
+    (or higher).
 
 In :file:`.htaccess`: