[HttpClient] Mention extra.trace_content option

Author: Mathieu Lechat

http_client.rst

@@ -814,6 +814,21 @@ ensure local networks are made inaccessible to the HTTP client::
     // but all the other requests, including other internal networks, will be allowed
     $client = new NoPrivateNetworkHttpClient(HttpClient::create(), ['104.26.14.0/23']);
 
+Profiling
+~~~~~~~~~
+
+When you are using the :class:`Symfony\\Component\\HttpClient\\TraceableHttpClient`
+responses content will be kept in memory, which can cause different issues.
+
+You can disable this behavior by setting the ``extra.trace_content`` to ``false``
+in your requests’ options::
+
+    $response = $client->request('GET', 'https://...', [
+        'extra' => ['trace_content' => false],
+    ]);
+
+This setting won’t have any effect with other clients.
+
 Performance
 -----------