doc: add section on memory feedback

doc/chapters/perf-feedback.texi

@@ -11,6 +11,7 @@
 * Off-line::                    Off-line performance feedback
 * Codelet performance::         Performance of codelets
 * Theoretical lower bound on execution time API::  
+* Memory feedback::             
 @end menu
 
 @node On-line
@@ -433,3 +434,61 @@ Emit statistics of actual execution vs theoretical upper bound. @var{integer}
 permits to choose between integer solving (which takes a long time but is
 correct), and relaxed solving (which provides an approximate solution).
 @end deftypefun
+
+@node Memory feedback
+@section Memory feedback
+
+It is possible to display memory usage at the end of the
+execution of your application. It allows to check all data allocated
+by StarPU have been cleared. To do so, you need to pass the option
+@code{--enable-memory-status} when running configure, and to set the
+environment variable @code{STARPU_MEMORY_STATS} when running the
+application.
+
+For example, if you do not unregister data at the end of the complex
+example, you will get something similar to:
+
+@example
+$ STARPU_MEMORY_STATS=1 ./examples/interface/complex
+...
+Memory status :
+#-------
+Data on Node #3
+#-----
+Data : 0x553ff40
+Size : 16
+
+#--
+Data access stats
+/!\ Work Underway
+Node #0
+	Direct access : 4
+	Loaded (Owner) : 0
+	Loaded (Shared) : 0
+	Invalidated (was Owner) : 0
+
+Node #3
+	Direct access : 0
+	Loaded (Owner) : 0
+	Loaded (Shared) : 1
+	Invalidated (was Owner) : 0
+
+#-----
+Data : 0x5544710
+Size : 16
+
+#--
+Data access stats
+/!\ Work Underway
+Node #0
+	Direct access : 2
+	Loaded (Owner) : 0
+	Loaded (Shared) : 1
+	Invalidated (was Owner) : 1
+
+Node #3
+	Direct access : 0
+	Loaded (Owner) : 1
+	Loaded (Shared) : 0
+	Invalidated (was Owner) : 0
+@end example