Update processors.rst

Author: noniagriconomie

logging/processors.rst

@@ -1,9 +1,9 @@
 How to Add extra Data to Log Messages via a Processor
 =====================================================
 
-Monolog allows you to process the record before logging it to add some
-extra data. A processor can be applied for the whole handler stack or
-only for a specific handler.
+Monolog allows you to process every record before logging it by adding some
+extra data. This is the role of a processor, which can be applied for the whole
+handler stack or only for a specific handler or channel.
 
 A processor is a callable receiving the record as its first argument.
 Processors are configured using the ``monolog.processor`` DIC tag. See the
@@ -46,6 +46,11 @@ using a processor::
         }
     }
 
+.. note::
+
+    As every log record is process by all registred processors, you must be very careful when you create one processor.
+    It has to be an optimized process, to not introduce any overhead.
+
 Next, register your class as a service, as well as a formatter that uses the extra
 information: